Revert "minuitwrp: drm: wait for last page flip to complete"

See https://github.com/omnirom/android_bootable_recovery/issues/219

This reverts commit 34ad728823b186f93016387f39388cdbde35b3ed.

Change-Id: Ia659b49af8206ba74b098aa721099a180762bab5
diff --git a/minuitwrp/graphics_drm.cpp b/minuitwrp/graphics_drm.cpp
index aaa9e4e..c321bb7 100644
--- a/minuitwrp/graphics_drm.cpp
+++ b/minuitwrp/graphics_drm.cpp
@@ -42,7 +42,6 @@
 
 static drm_surface *drm_surfaces[2];
 static int current_buffer;
-static bool flip_pending = false;
 static GRSurface *draw_buf = NULL;
 
 static drmModeCrtc *main_monitor_crtc;
@@ -481,36 +480,18 @@
     return draw_buf;
 }
 
-static void drm_page_flip_event(int fd, unsigned int frame, unsigned int sec,
-        unsigned int usec, void *data) {
-    flip_pending = false;
-}
-
 static GRSurface* drm_flip(minui_backend* backend __unused) {
     int ret;
-    drmEventContext ev;
-
-    memset(&ev, 0, sizeof(ev));
-
     memcpy(drm_surfaces[current_buffer]->base.data,
             draw_buf->data, draw_buf->height * draw_buf->row_bytes);
 
-    ev.version = 2;
-    ev.page_flip_handler = drm_page_flip_event;
-
-    /* wait for previous page flip, if any, to complete */
-    while (flip_pending) {
-        drmHandleEvent(drm_fd, &ev);
-    }
 
     ret = drmModePageFlip(drm_fd, main_monitor_crtc->crtc_id,
-                          drm_surfaces[current_buffer]->fb_id, DRM_MODE_PAGE_FLIP_EVENT, NULL);
+                          drm_surfaces[current_buffer]->fb_id, 0, NULL);
     if (ret < 0) {
         printf("drmModePageFlip failed ret=%d\n", ret);
         return NULL;
     }
-
-    flip_pending = true;
     current_buffer = 1 - current_buffer;
     return draw_buf;
 }