arm: Fix constraints in MVE asrl and lsll patterns [PR122858]

arm: Fix constraints in MVE asrl and lsll patterns [PR122858]

The second alternative for operand 1 needs a new constraint which does
not overlap with Pg, except that it can handle 32 to generate an
optimal mov.

This patch introduces a new Ph constraint which has the [32..255]
range.

This fixes a lot of regressions when running the testsuite for an MVE
target such as -march=armv8.1-m.main+mve.fp+fp.dp -mfloat-abi=hard.

gcc/ChangeLog:

	PR target/122858
	* config/arm/constraints.md (Ph): New constraint.
	* config/arm/mve.md (mve_asrl_imm, mve_lsll_imm): Fix constraints
	of operand 1 and handle 32 as special shift amount.

gcc/testsuite/ChangeLog:

	PR target/122858
	* gcc.target/arm/mve/pr122858.c: New test.