drm/bridge: anx7625: check the return on anx7625_aux_trans

Clang static analysis reports this issue
anx7625.c:876:13: warning: The left operand of '&' is
  a garbage value
  if (!(bcap & 0xOA01)) {
        ~~~~ ^

bcap is only set by a successful call to
anx7625_aux_trans().  So check.

Fixes: cd1637c7 ("drm/bridge: anx7625: add HDCP support")
Signed-off-by: Tom Rix <trix@redhat.com>
Fixes: adca62ec ("drm/bridge: anx7625: Support reading edid through aux channel")
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220303201943.501746-1-trix@redhat.comReviewed-by: Robert Foss <robert.foss@linaro.org>

drivers/gpu/drm/bridge/analogix/anx7625.c

@@ -874,7 +874,10 @@ static int anx7625_hdcp_enable(struct anx7625_data *ctx)
 	}
 
 	/* Read downstream capability */
-	anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
+	ret = anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
+	if (ret < 0)
+		return ret;
+
 	if (!(bcap & 0x01)) {
 		pr_warn("downstream not support HDCP 1.4, cap(%x).\n", bcap);
 		return 0;