AVX-512: Pacify -Wshift-overflow=2. [PR115409]

AVX-512: Pacify -Wshift-overflow=2. [PR115409]

A shift of 31 on a signed int is undefined behavior.  Since unsigned
int is 32-bits wide this change fixes it and silences the warning.

gcc/ChangeLog:

	PR target/115409
	* config/i386/avx512fp16intrin.h (_mm512_conj_pch): Make the
	constant unsigned before shifting.
	* config/i386/avx512fp16vlintrin.h (_mm256_conj_pch): Likewise.
	(_mm_conj_pch): Likewise.

Signed-off-by: Collin Funk <collin.funk1@gmail.com>