arm/66791: Replace builtins in vceq_* (a, b) with a == b.

arm/66791: Replace builtins in vceq_* (a, b) with a == b.

gcc/ChangeLog:
	* config/arm/arm_neon.h (vceq_s8): Replace builtin with __a == __b.
	(vceq_s16): Likewise.
	(vceq_s32): Likewise.
	(vceq_u8): Likewise.
	(vceq_u16): Likewise.
	(vceq_u32): Likewise.
	(vceq_p8): Likewise.
	(vceqq_s8): Likewise.
	(vceqq_s16): Likewise.
	(vceqq_s32): Likewise.
	(vceqq_u8): Likewise.
	(vceqq_u16): Likewise.
	(vceqq_u32): Likewise.
	(vceqq_p8): Likewise.
	(vceq_f32): Gate __a == __b on __FAST_MATH__.
	(vceqq_f32): Likewise.
	(vceq_f16): Likewise.
	(vceqq_f16): Likewise.