aarch64: Add flags field to aarch64-simd-pragma-builtins.def

aarch64: Add flags field to aarch64-simd-pragma-builtins.def

This patch adds a flags field to aarch64-simd-pragma-builtins.def
and uses it to add attributes to the function declaration.

gcc/
	* config/aarch64/aarch64-simd-pragma-builtins.def: Add a flags
	field to each entry.
	* config/aarch64/aarch64-builtins.cc: Update includes accordingly.
	(aarch64_pragma_builtins_data): Add a flags field.
	(aarch64_init_pragma_builtins): Use the flags field to add attributes
	to the function declaration.