LoongArch: Expand left rotate to right rotate with negated amount

gcc/ChangeLog:

	* config/loongarch/loongarch.md (rotl<mode>3):
	New define_expand.
	* config/loongarch/simd.md (vrotl<mode>3): Likewise.
	(rotl<mode>3): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/rotl-with-rotr.c: New test.
	* gcc.target/loongarch/rotl-with-vrotr-b.c: New test.
	* gcc.target/loongarch/rotl-with-vrotr-h.c: New test.
	* gcc.target/loongarch/rotl-with-vrotr-w.c: New test.
	* gcc.target/loongarch/rotl-with-vrotr-d.c: New test.
	* gcc.target/loongarch/rotl-with-xvrotr-b.c: New test.
	* gcc.target/loongarch/rotl-with-xvrotr-h.c: New test.
	* gcc.target/loongarch/rotl-with-xvrotr-w.c: New test.
	* gcc.target/loongarch/rotl-with-xvrotr-d.c: New test.