tests: use drmtest_skip to check for rings

To simplify things add a set of gem_check_<ring> functions which take
care of this. Since I've opted for static inlines drmtest.h grew a few
more header includes which was a neat opportunity to dump a few redundant
#defines.

This kills all the skipped_all hand-rolled logic we have.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/gem_ctx_bad_exec.c

@@ -104,7 +104,6 @@ static int exec(int fd, uint32_t handle, int ring, int ctx_id)
 	return ret;
 }
 
-#define MI_BATCH_BUFFER_END	(0xA<<23)
 int main(int argc, char *argv[])
 {
 	uint32_t handle;