drm/amd/display: do not allocate display_mode_lib unnecessarily

This allocation isn't required and can fail when resuming from suspend.

Bug: https://gitlab.freedesktop.org/drm/amd/issues/1009Signed-off-by: Dor Askayo <dor.askayo@gmail.com>
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -2462,12 +2462,7 @@ void dc_set_power_state(
 	enum dc_acpi_cm_power_state power_state)
 {
 	struct kref refcount;
-	struct display_mode_lib *dml = kzalloc(sizeof(struct display_mode_lib),
-						GFP_KERNEL);
-
-	ASSERT(dml);
-	if (!dml)
-		return;
+	struct display_mode_lib *dml;
 
 	switch (power_state) {
 	case DC_ACPI_CM_POWER_STATE_D0:
@@ -2490,6 +2485,12 @@ void dc_set_power_state(
 		 * clean state, and dc hw programming optimizations will not
 		 * cause any trouble.
 		 */
+		dml = kzalloc(sizeof(struct display_mode_lib),
+				GFP_KERNEL);
+
+		ASSERT(dml);
+		if (!dml)
+			return;
 
 		/* Preserve refcount */
 		refcount = dc->current_state->refcount;
@@ -2503,10 +2504,10 @@ void dc_set_power_state(
 		dc->current_state->refcount = refcount;
 		dc->current_state->bw_ctx.dml = *dml;
 
+		kfree(dml);
+
 		break;
 	}
-
-	kfree(dml);
 }
 
 void dc_resume(struct dc *dc)