disp: msm: avoid using #ifdef for configurations

Use #if IS_ENABLED() instead of #ifdef for configurations as vendor module
guidelines.

Use #if IS_ENABLED(CONFIG_XXX) instead of #ifdef CONFIG_XXX to ensure that
the code inside the #if block continues to compile if the config changes
to a tristate config in the future.

The differences are as follows:
	1.#if IS_ENABLED(CONFIG_XXX) evaluates to true when CONFIG_XXX is set to
		module (=m) or built-in (=y).
	2.#ifdef CONFIG_XXX evaluates to true when CONFIG_XXX is set to
		built-in(=y) , but doesn't when CONFIG_XXX is set to module(=m).
		Use this only when you're certain you want to do the same thing
		when the config is set to module or is disabled.

Change-Id: Ia806b9b01ad8414d0e4de027a382cb68e7fb4a6a
Signed-off-by: GG Hou <quic_renjhou@quicinc.com>

msm/sde/sde_kms.c

@@ -123,7 +123,7 @@ bool sde_is_custom_client(void)
 	return sdecustom;
 }
 
-#ifdef CONFIG_DEBUG_FS
+#if IS_ENABLED(CONFIG_DEBUG_FS)
 void *sde_debugfs_get_root(struct sde_kms *sde_kms)
 {
 	struct msm_drm_private *priv;
@@ -211,7 +211,7 @@ static int _sde_kms_dump_clks_state(struct sde_kms *sde_kms)
 {
 	return 0;
 }
-#endif
+#endif /* CONFIG_DEBUG_FS */
 
 static void sde_kms_wait_for_frame_transfer_complete(struct msm_kms *kms,
 		struct drm_crtc *crtc)