drm/radeon/r100: Clean up errors in r100.c

Fix the following errors reported by checkpatch:

ERROR: spaces required around that '+=' (ctx:VxV)o
Signed-off-by: GuoHua Chen <chenguohua_716@163.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/r100.c

@@ -1327,7 +1327,7 @@ int r100_packet3_load_vbpntr(struct radeon_cs_parser *p,
 	    return -EINVAL;
 	}
 	track->num_arrays = c;
-	for (i = 0; i < (c - 1); i+=2, idx+=3) {
+	for (i = 0; i < (c - 1); i += 2, idx += 3) {
 		r = radeon_cs_packet_next_reloc(p, &reloc, 0);
 		if (r) {
 			DRM_ERROR("No reloc for packet3 %d\n",