LoongArch: Add tests for ASX vector xvsll/xvsrl instructions.
gcc/testsuite/ChangeLog:
* gcc.target/loongarch/vector/lasx/lasx-xvsll.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvslli.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsllwil-1.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsllwil-2.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrl.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrli.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrln.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrlni.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrlr.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrlri.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrlrn.c: New test.
* gcc.target/loongarch/vector/lasx/lasx-xvsrlrni.c: New test.