i386: Support vectorized BF16 add/sub/mul/div with AVX10.2 instructions

i386: Support vectorized BF16 add/sub/mul/div with AVX10.2 instructions

AVX10.2 introduces several non-exception instructions for BF16 vector.
Enable vectorized BF add/sub/mul/div operation by supporting standard
optab for them.

gcc/ChangeLog:

	* config/i386/sse.md (div<mode>3): New expander for BFmode div.
	(VF_BHSD): New mode iterator with vector BFmodes.
	(<insn><mode>3<mask_name><round_name>): Change mode to VF_BHSD.
	(mul<mode>3<mask_name><round_name>): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/avx10_2-512-bf-vector-operations-1.c: New test.
	* gcc.target/i386/avx10_2-bf-vector-operations-1.c: Ditto.