[cpu-detection] Copy simplified version of get_cpuid_max to remove dependency...

[cpu-detection] Copy simplified version of get_cpuid_max to remove dependency to clang's implementation

Summary:
Attempting to fix PR30384.
Take the same approach as in compiler_rt and add a simplified version of __get_cpuid_max.
Including cpuid.h is no longer needed.

Reviewers: echristo, joerg

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24597

llvm-svn: 283265