i386: Do not check vector size conflict when AVX512 is not explicitly set [PR 118815]

i386: Do not check vector size conflict when AVX512 is not explicitly set [PR 118815]

When AVX512 is not explicitly set, we should not take EVEX512 bit into
consideration when checking vector size. It will solve the intrin header
file reporting warnings when compiling with -Wsystem-headers.

However, there is side effect on the usage for '-march=xxx -mavx10.1-256',
where xxx is with AVX512. It will not report warning on vector size for now.
Since it is a rare usage, we will take it.

gcc/ChangeLog:

	PR target/118815
	* config/i386/i386-options.cc (ix86_option_override_internal):
	Do not check vector size conflict when AVX512 is not explicitly
	set.

gcc/testsuite/ChangeLog:

	PR target/118815
	* gcc.target/i386/pr118815.c: New test.