tests|lib: remove assert.h includes

Only the igt core and non-test tools should have asserts to catch
internal errors, tests and helper libraries should all user igt_asert
instead.

Fix things up where assert instead of igt_assert was used.

One tiny step towards header sanity.

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

lib/ioctl_wrappers.c

@@ -808,7 +808,7 @@ void gem_require_ring(int fd, int ring_id)
 		return;
 #endif
 	default:
-		assert(0);
+		igt_assert(0);
 		return;
 	}
 }