aarch64: Add support for unpacked SVE ABD

aarch64: Add support for unpacked SVE ABD

This patch adds support for unpacked SVE SABD and UABD.
It also rewrites the patterns so that they match as combine
patterns without the need for REG_EQUAL notes.  Finally,
there was no pattern for merging with the second input,
which can be handled by reversing the operands.

The type suffix needs to be taken from the element size rather
than the container size.

gcc/
	* config/aarch64/aarch64-sve.md (<su>abd<mode>_3): Extend from
	SVE_FULL_I to SVE_I.
	(*aarch64_cond_<su>abd<mode>_2): Likewise.
	(*aarch64_cond_<su>abd<mode>_any): Likewise.
	(@aarch64_pred_<su>abd<mode>): Likewise.  Use UNSPEC_PRED_X
	for the max and min but not for the minus.
	(*aarch64_cond_<su>abd<mode>_3): New pattern.

gcc/testsuite/
	* g++.target/aarch64/sve/abd_1.C: New test.
	* g++.target/aarch64/sve/cond_abd_1.C: Likewise.
	* g++.target/aarch64/sve/cond_abd_2.C: Likewise.
	* g++.target/aarch64/sve/cond_abd_3.C: Likewise.
	* g++.target/aarch64/sve/cond_abd_4.C: Likewise.