[libclc] libclc: Update atan2 (PR #188706)

[Karol Herbst via cfe-commits]

karolherbst wrote:

> > this PR breaks atan2:
> > `ERROR: atan2: -3294199.000000 ulp error at {-0x1.fffffep+127 (0xff7fffff), -0x1.fffffep+127 (0xff7fffff)}: *-0x1.2d97c8p+1 vs. -0x1.921fb6p+1 (0xc0490fdb) at index: 198`
> 
> On what, with what? Can you post the compiler output? If I interpret the IR with these values, I get the expected result

Tested on Intel with rusticl. Though atm we don't support denorms with fp32 and I'm wondering if that's related? I found a couple of other regressions and created reverts for those for now until I have time to dig into it: #189781 

But could also be just some hardware inaccuracy or something else.

https://github.com/llvm/llvm-project/pull/188706