fbcon: Block rounding off mode for VT running X.

fbcon: Block rounding off mode for VT running X.

When X is active i.e. GNOME/Ubuntu Desktop is running, fb_display
does not get updated and still contain stale values of unplug event.
Rounding mode of stale values causes wrong resolution being picked up
on hotplugging HDMI.

Bug 200295792

Change-Id: Icdd4d1ea06044ac63e3b76d881e4d7ccc65bf5fd
Signed-off-by: Saket Sinha <sakets@nvidia.com>
Reviewed-on: http://git-master/r/1490339
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>