perf test: Fix sys_enter_openat event test for musl

perf test: Fix sys_enter_openat event test for musl

The "syscalls:sys_enter_openat event fields" test calls

openat(AT_FDCWD, "/etc/passwd", O_RDONLY | O_DIRECTORY)

and verifies that the flags of the captured event are matching.
This fails for musl, where the openat syscall wrapper always adds
O_LARGEFILE.

Update the check to allow for additional flags, the access mode flags
must be unchanged.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>