The evidence of what? The rumour that they're oh so desperate to get into console market that they'll gift Nintendo the hardware comes straight from SA. That rumour is most likely wrong. The reports that NX is being based on Tegra are probably right though.
Console licensing deal won't "salvage" any business for them. And it's a stretch already to assume that Tegra business needs salvaging.
Nvidia is not desperate for a console market. Tegra however, does need an actual customer if the business unit is to continue its existence in any meaningful way. The unit had a 239 million USD loss in YE Jan. 2016, and a 254 million USD loss in YE Jan. 2015, and a 268 million USD loss in YE Jan. 2014 against a 40 million USD income in YE Jan. 2013. (p. 88 AR15 - consolidated financials and p. 89 AR16) .
Is that a disaster - probably not, Nvidia as a whole is making good money on enthusiast 3d and computing power for large supercomputers.
On the other hand, looking at Nvidia's business long term - they are not in an enviable position (it's worse for AMD but that doesn't help Nvidia much). The PC market for 3d graphics is contracting. Luckily Nvidia has found ways to squeeze more money out of it.
However, for a sustainable and healthy long to very long term business Nvidia would really like a somewhat more diversified revenue stream. And that's where Tegra comes into play. It allows them to leverage similar technology in a different segment.
And sure, the Tegra unit have some automotive costumers. And sure, they are somewhat of a player in self-driving cars. Guess what, the latter is currently a small experimental segment and the industry as a whole (automotive) is known for slim margins - a fact noted by Nvidia in AR15 themselves.
Would Nvidia be giving everything to Nintendo for free? Nope. Would Nvidia be willing to live on slim margins for a single project in order to get some value out of a relationship they by how have spent more than 5 years on, and which will furthermore serve as a useful example that they can deliver good semi-custom in high unit numbers? You bet they will.
They want to have an example like that to shop around for other businesses. Currently, none of their large scale semi-custom examples (both in the console business) are recent, or even examples that make Nvidia look good.
In the end, does this mean Nvidia is doomed? No. Does it mean that Tegra is useless? No. It means that if the Tegra unit doesn't change what it have been doing Nvidia might simply cut down on internal funding and channel those to some other alternative ventures with better long term outlooks.
Finally, on the whole question of if the deal is good or bad for Nvidia. Nvidia has a few good options here. They have a very large internal software stack that they could leverage as a way to entice Nintendo. eg. you buy Tegra we throw in compilers, debug suite, specialised analysis tools and some help communicating with the big engine makers. That costs Nvidia little, Nintendo gains a lot. How it affects the deal depends on how you look at the value of the service.
In short:
Nvidia doomed? No!
Tegra is doomed? not yet!
Nvidia give Nintendo money for this deal? Probably not
Nvidia is getting Geforce money out of this deal? I doubt it.
Nvidia is getting a working somewhat succesful semi-custom deal to show other potential costumers? Probably