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/prime_self_import.c

@@ -51,8 +51,6 @@
 
 #define BO_SIZE (16*1024)
 
-#define ARRAY_SIZE(x)	(sizeof(x) / sizeof((x)[0]))
-
 static char counter;
 volatile int pls_die = 0;