drm/amd/display: Add missing NULL pointer check within dpcd_extend_address_range

[Why & How]
ASSERT if return NULL from kcalloc.
Reviewed-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@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/link/protocols/link_dpcd.c

@@ -165,6 +165,7 @@ static void dpcd_extend_address_range(
 		*out_address = new_addr_range.start;
 		*out_size = ADDRESS_RANGE_SIZE(new_addr_range.start, new_addr_range.end);
 		*out_data = kcalloc(*out_size, sizeof(**out_data), GFP_KERNEL);
+		ASSERT(*out_data);
 	}
 }