drm/bridge: analogix: Don't return -EINVAL when panel doesn't support PSR

We will ignored PSR setting if panel not support it. So, in this case,
we should return from analogix_dp_enable/disable_psr() without any
error code. Let's retrun 0 instead of -EINVAL when panel not support PSR
in analogix_dp_enable/disable_psr().

Signed-off-by: zain wang <[e-mail]>
Signed-off-by: Archit Taneja <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

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

···
 	struct edp_vsc_psr psr_vsc;
 
 	if (!dp->psr_support)
-		return -EINVAL;
+		return 0;
 
 	/* Prepare VSC packet as per EDP 1.4 spec, Table 6.9 */
 	memset(&psr_vsc, 0, sizeof(psr_vsc));
···
 	struct edp_vsc_psr psr_vsc;
 
 	if (!dp->psr_support)
-		return -EINVAL;
+		return 0;
 
 	/* Prepare VSC packet as per EDP 1.4 spec, Table 6.9 */
 	memset(&psr_vsc, 0, sizeof(psr_vsc));