aarch64: Fix RTL patterns for UABA/SABA

aarch64: Fix RTL patterns for UABA/SABA

Sometime ago we changed the RTL representation of the (SU)ABD
instructions in RTL to a (MINUS (MAX) (MIN)) rather than a (MINUS (ABS) (ABS))
as it is more correctly models the semantics.
We should do the same for the accumulation forms of these instructions:
UABA/SABA.

This patch does that and allows the new pattern to generate the unsigned
UABA form as well.
The new form also allows it to more easily be re-used to implement the
relevant arm_neon.h intrinsics in the future.

The testcase takes an -fno-tree-reassoc to work around a side-effect of
PR98581.

gcc/
	* config/aarch64/aarch64-simd.md (aba<mode>_3): Rename to...
	(aarch64_<su>aba<mode>): ... This.  Handle uaba as well.
	Change RTL pattern to match.

gcc/testsuite/
	* gcc.target/aarch64/usaba_1.c: New test.