[Driver,X86] Ignore -mfpmath= for assembler input

Some options are only claimed in AddX86TargetArgs/etc (called by
Clang::RenderTargetOptions).
For assembler input, `Add*TargetArgs` is not called. If an option is
unclaimed, it either leads to a -Wunused-command-line-argument warning
or an error (if `TargetSpecific` is set)
```
// clang '-###' --target=x86_64 -mfpmath=sse -c a.s
clang: error: unsupported option '-mfpmath=sse' for target 'x86_64'
```

For -mfpmath=, it's actually claimed by RenderFloatingPointOptions,
which should be moved to AddARMTargetArgs/AddX86TargetArgs later
(non-AArch32-non-x86 targets give a frontend error).
This change is localized and similar to D153691, for release/17.x
backporting.

Fix https://github.com/llvm/llvm-project/issues/65023

Reviewed By: thesamesam

Differential Revision: https://reviews.llvm.org/D159010