[display] Fix corruption in color lcd update, again.
[display] Fix corruption in color lcd update, again.

The previous attempt didn't completely resolve the issue.
Adjusting the baud rate prescaler seems solid.
Tested with svg_test on mono and color memory lcds.

R=travisg@gmail.com

Review URL: https://codereview.chromium.org/1822123004 .

travisg/lk,littlekernel/lk,travisg/lk,travisg/lk,hollanderic/lkstuff,minglun-tsai/lk,minglun-tsai/lk,littlekernel/lk,littlekernel/lk,hollanderic/lkstuff,hollanderic/lkstuff,minglun-tsai/lk,travisg/lk,minglun-tsai/lk,hollanderic/lkstuff,littlekernel/lk