kms_vaapi: add cursor capture for amd/intel monitor capture

Always find largest drm buf, to fix some cases
when there are multiple planes and we accidentally
capture a drm buf that isn't the target buf.
We always want the full SCREEN drm buf.

include/capture/kms_vaapi.h

@@ -9,7 +9,6 @@
 typedef struct _XDisplay Display;
 
 typedef struct {
-    Display *dpy;
     const char *display_to_capture; /* if this is "screen", then the entire x11 screen is captured (all displays). A copy is made of this */
     gsr_gpu_info gpu_inf;
     const char *card_path; /* reference */