RISC-V: Cache Management Operation instructions testcases

RISC-V: Cache Management Operation instructions testcases

This commit adds testcases about CMO instructions.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/cmo-zicbom-1.c: New test.
	* gcc.target/riscv/cmo-zicbom-2.c: New test.
	* gcc.target/riscv/cmo-zicbop-1.c: New test.
	* gcc.target/riscv/cmo-zicbop-2.c: New test.
	* gcc.target/riscv/cmo-zicboz-1.c: New test.
	* gcc.target/riscv/cmo-zicboz-2.c: New test.