Add USB keyboard/mouse support for Cheri NetSurf.

This change disables the MTL touch screen support and adds USB
keyboard and mouse support.  Currently it assumes the mouse is
/dev/ums0 (moused is not running) and the keyboard is /dev/ttyv0.
Force NetSurf to only be 720 pixels wide for the HDMI monitor.

This change forces NetSurf to be only 720 pixels wide so it is
not cut off by the HDMI monitor.
Fix scroll corruption bug.

This change is a workaround for a bug with scrolling.  It forces
a redraw at the boundries.