disp: msm: dp: compile MST feature based on display config

Add a compile time flag for the MST feature that will allow
selectively enabling the feature.

Change-Id: I8bf288277c7af00c3cf254a8c757151559e0a010
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>

msm/sde/sde_kms.c

@@ -37,6 +37,7 @@
 #include "sde_wb.h"
 #include "dp_display.h"
 #include "dp_drm.h"
+#include "dp_mst_drm.h"
 
 #include "sde_kms.h"
 #include "sde_core_irq.h"