staging/xgifb: Rename panel defines and remove duplicated defines

staging/xgifb: Rename panel defines and remove duplicated defines

This patch renames the Panel* defines and their usage to the naming
convention of the sis initdef.h and removes the now duplicated defines.

Renames:
Panel320x480 -> Panel_320x480
Panel800x600 -> Panel_800x600
Panel1024x768 -> Panel_1024x768
Panel1024x768x75 -> Panel_1024x768x75
Panel1280x1024 -> Panel_1280x1024
Panel1280x1024x75 -> Panel_1280x1024x75
Panel1280x960 -> Panel_1280x960
Panel1400x1050 -> Panel_1400x1050
Panel1600x1200 -> Panel_1600x1200

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>