AArch64: Use FLOAT_MODE_P macro and add FLAG_AUTO_FP [PR94442]

AArch64: Use FLOAT_MODE_P macro and add FLAG_AUTO_FP [PR94442]

Since all FP intrinsics are set by FLAG_FP by default, but not all FP intrinsics
raise FP exceptions or read FPCR register.  So we add a global flag FLAG_AUTO_FP
to suppress the flag FLAG_FP.

2020-08-04  Zhiheng Xie  <xiezhiheng@huawei.com>

gcc/ChangeLog:

	* config/aarch64/aarch64-builtins.c (aarch64_call_properties):
	Use FLOAT_MODE_P macro instead of enumerating all floating-point
	modes and add global flag FLAG_AUTO_FP.