OMAP: DSS2: Make partial update width even

There are some strange problems with DSI and updates with odd widths. One
particular problem is that HS TX timeout triggers easily with updates with
odd widths.

This patch makes the updates widths even, circumventing the problem. There
should be no ill side effects with increasing the update area slightly to
make the width even.

Signed-off-by: Ville Syrjälä <ville.syrjala@nokia.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>