drm/atomic-helper: Bump vblank timeout to 100 ms

The 50 ms default timeout waiting for vblanks is too small
for the first vblank from the ST-Ericsson MCDE display
controller over DSI. Presumably this is because the DSI
display is command-mode only and the state machine will
take some time setting up its state for the first display
update, and we hit a timeout. 100 ms makes it pass without
problems.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190430093746.26485-1-linus.walleij@linaro.org

drivers/gpu/drm/drm_atomic_helper.c

@@ -1424,7 +1424,7 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
 		ret = wait_event_timeout(dev->vblank[i].queue,
 				old_state->crtcs[i].last_vblank_count !=
 					drm_crtc_vblank_count(crtc),
-				msecs_to_jiffies(50));
+				msecs_to_jiffies(100));
 
 		WARN(!ret, "[CRTC:%d:%s] vblank wait timed out\n",
 		     crtc->base.id, crtc->name);