aarch64: Add support for unpacked SVE FDIV

aarch64: Add support for unpacked SVE FDIV

This patch extends the unpredicated FP division expander to support
partial FP modes.  It extends the existing patterns used to implement
UNSPEC_COND_FDIV and it's approximation as needed.

gcc/ChangeLog:

	* config/aarch64/aarch64-sve.md: (@aarch64_sve_<optab><mode>):
	Extend from SVE_FULL_F to SVE_F, use aarch64_predicate_operand.
	(@aarch64_frecpe<mode>): Extend from SVE_FULL_F to SVE_F.
	(@aarch64_frecps<mode>): Likewise.
	(div<mode>3): Likewise, use aarch64_sve_fp_pred.
	* config/aarch64/iterators.md: Add warnings above SVE_FP_UNARY
	and SVE_FP_BINARY.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/unpacked_fdiv_1.c: New test.
	* gcc.target/aarch64/sve/unpacked_fdiv_2.c: Likewise.
	* gcc.target/aarch64/sve/unpacked_fdiv_3.c: Likewise.