drm: display: Fix duplicate field initialization in dcn31

Fix the following coccicheck warning:
drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c:917:56-57:
pstate_enabled: first occurrence line 935, second occurrence line 937

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Wan Jiabing

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c

@@ -934,7 +934,6 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.dmub_command_table = true,
 	.pstate_enabled = true,
 	.use_max_lb = true,
-	.pstate_enabled = true,
 	.enable_mem_low_power = {
 		.bits = {
 			.vga = false,