media: camss-vfe: always initialize reg at vfe_set_xbar_cfg()

if output->wm_num is bigger than 2, the value for reg is
not initialized, as warned by smatch:
	drivers/media/platform/qcom/camss-8x16/camss-vfe.c:633 vfe_set_xbar_cfg() error: uninitialized symbol 'reg'.
	drivers/media/platform/qcom/camss-8x16/camss-vfe.c:637 vfe_set_xbar_cfg() error: uninitialized symbol 'reg'.

That shouldn't happen in practice, so add a logic that will
break the loop if i > 1, fixing the warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Todor Tomov <todor.tomov@linaro.org>

drivers/media/platform/qcom/camss-8x16/camss-vfe.c

@@ -622,6 +622,9 @@ static void vfe_set_xbar_cfg(struct vfe_device *vfe, struct vfe_output *output,
 			reg = VFE_0_BUS_XBAR_CFG_x_M_PAIR_STREAM_EN;
 			if (p == V4L2_PIX_FMT_NV12 || p == V4L2_PIX_FMT_NV16)
 				reg |= VFE_0_BUS_XBAR_CFG_x_M_PAIR_STREAM_SWAP_INTER_INTRA;
+		} else {
+			/* On current devices output->wm_num is always <= 2 */
+			break;
 		}
 
 		if (output->wm_idx[i] % 2 == 1)