drm/amd/display: Clear cached watermark after resume

[WHY]
Driver could skip program watermarks when resume from S0i3/S4.

[HOW]
Clear the cached one first to make sure new value gets applied.
Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Roman Li <roman.li@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c

@@ -545,6 +545,7 @@ static void hubbub35_init(struct hubbub *hubbub)
 			DCHUBBUB_ARB_MAX_REQ_OUTSTAND, 256,
 			DCHUBBUB_ARB_MIN_REQ_OUTSTAND, 256);
 
+	memset(&hubbub2->watermarks.a.cstate_pstate, 0, sizeof(hubbub2->watermarks.a.cstate_pstate));
 }
 
 /*static void hubbub35_set_request_limit(struct hubbub *hubbub,