gallium/radeon: fixed division by zero

Coverity is getting a false positive that a division by zero can occur
here. This change will silence the Coverity warnings as a division by zero
cannot occur in this case.

Signed-off-by: Jakob Sinclair <sinclair.jakob@openmailbox.org>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/drivers/radeon/r600_test_dma.c

@@ -345,6 +345,9 @@ void r600_test_dma(struct r600_common_screen *rscreen)
 					dstx = rand() % (tdst.width0 - width + 1) & ~0x7;
 					dsty = rand() % (tdst.height0 - height + 1) & ~0x7;
 				} else {
+					/* just make sure that it doesn't divide by zero */
+					assert(max_width > 0 && max_height > 0);
+
 					width = (rand() % max_width) + 1;
 					height = (rand() % max_height) + 1;