tests: roll out igt_simple_init/igt_simple_main

Also use igt_skip a bit more to simplify some of the tests.

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

tests/gem_set_tiling_vs_pwrite.c

@@ -46,7 +46,7 @@
  * Testcase: Check set_tiling vs pwrite coherency
  */
 
-int main(int argc, char **argv)
+igt_simple_main
 {
 	int fd;
 	uint32_t *ptr;
@@ -94,6 +94,4 @@ int main(int argc, char **argv)
 	munmap(ptr, OBJECT_SIZE);
 
 	close(fd);
-
-	return 0;
 }