drm/radeon: possible buffer overflow

Buffer 'afmt_status' of size 6 could overflow, since index 'afmt_idx' is
checked after access.

Fixes: 5cc4e5fc ("drm/radeon: Cleanup HDMI audio interrupt handling for evergreen")
Co-developed-by: Ivanov Mikhail <ivanov.mikhail1@huawei-partners.com>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -4821,14 +4821,15 @@ int evergreen_irq_process(struct radeon_device *rdev)
 			break;
 		case 44: /* hdmi */
 			afmt_idx = src_data;
-			if (!(afmt_status[afmt_idx] & AFMT_AZ_FORMAT_WTRIG))
-				DRM_DEBUG("IH: IH event w/o asserted irq bit?\n");
-
 			if (afmt_idx > 5) {
 				DRM_ERROR("Unhandled interrupt: %d %d\n",
 					  src_id, src_data);
 				break;
 			}
+
+			if (!(afmt_status[afmt_idx] & AFMT_AZ_FORMAT_WTRIG))
+				DRM_DEBUG("IH: IH event w/o asserted irq bit?\n");
+
 			afmt_status[afmt_idx] &= ~AFMT_AZ_FORMAT_WTRIG;
 			queue_hdmi = true;
 			DRM_DEBUG("IH: HDMI%d\n", afmt_idx + 1);