fbdev: omapfb: remove omap1 osk driver

Commit 21a3e6ee

 ("ARM: omap1: remove osk-mistral add-on board
support") removed the platform_device definition for the "lcd_osk"
device, so this driver is now unused and can be removed as well.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Helge Deller <deller@gmx.de>