RISC-V: Fix test target selector

The previous target selector was not properly gating the tests to rv32
and rv64 targets. This was triggering an excess failure on rv32 targets
where it would try to run the zbc64 tests. Fix selector

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/crc-builtin-zbc32.c: Fix selector.
	* gcc.target/riscv/crc-builtin-zbc64.c: Ditto.

Signed-off-by: Edwin Lu <ewlu@rivosinc.com>