arm: PR target/109939 Correct signedness of return type of __ssat intrinsics

arm: PR target/109939 Correct signedness of return type of __ssat intrinsics

As the PR says we shouldn't be using qualifier_unsigned for the return type of the __ssat intrinsics.
UNSIGNED_SAT_BINOP_UNSIGNED_IMM_QUALIFIERS already exists for that.
This was just a thinko.
This patch fixes this and the warning with -Wconversion goes away.

Bootstrapped and tested on arm-none-linux-gnueabihf.

gcc/ChangeLog:

	PR target/109939
	* config/arm/arm-builtins.cc (SAT_BINOP_UNSIGNED_IMM_QUALIFIERS): Use
	qualifier_none for the return operand.

gcc/testsuite/ChangeLog:

	PR target/109939
	* gcc.target/arm/pr109939.c: New test.