drm/i915: Fix memory leak in intel_hdcp auth

Static code analysis tool reported memory leak in
intel_hdcp_auth_downstream. Fixing the memory leak.

v2: Rebase, move free to a cleanup label(Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180404225957.7457-1-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/intel_hdcp.c

@@ -435,7 +435,7 @@ int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
 
 	ret = shim->read_ksv_fifo(intel_dig_port, num_downstream, ksv_fifo);
 	if (ret)
-		return ret;
+		goto err;
 
 	/*
 	 * When V prime mismatches, DP Spec mandates re-read of
@@ -451,12 +451,15 @@ int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
 
 	if (i == tries) {
 		DRM_ERROR("V Prime validation failed.(%d)\n", ret);
-		return ret;
+		goto err;
 	}
 
 	DRM_DEBUG_KMS("HDCP is enabled (%d downstream devices)\n",
 		      num_downstream);
-	return 0;
+	ret = 0;
+err:
+	kfree(ksv_fifo);
+	return ret;
 }
 
 /* Implements Part 1 of the HDCP authorization procedure */