Simplify (AND (ASHIFTRT A imm) mask) to (LSHIFTRT A imm) for vector mode.

When mask is (1 << (prec - imm) - 1) which is used to clear upper bits
of A, then it can be simplified to LSHIFTRT.

i.e Simplify
(and:v8hi
  (ashifrt:v8hi A 8)
  (const_vector 0xff x8))
to
(lshifrt:v8hi A 8)

gcc/ChangeLog:

	PR target/114428
	* simplify-rtx.cc
	(simplify_context::simplify_binary_operation_1):
	Simplify (AND (ASHIFTRT A imm) mask) to (LSHIFTRT A imm) for
	specific mask.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr114428-1.c: New test.