bpf: testsuite: fix unresolved test in memset-1.c

bpf: testsuite: fix unresolved test in memset-1.c

The test was trying to do too much by both checking for an error, and
checking the resulting assembly. Of course, due to the error no asm was
produced, so the scan-asm went unresolved. Split it into two separate
tests to fix the issue.

gcc/testsuite/

	* gcc.target/bpf/memset-1.c: Move error test case to...
	* gcc.target/bpf/memset-2.c: ... here. New test.