linux-imx

OMAPFB: remove exported udpate window

omapfb contains an exported omapfb_update_window function, which, at
some point in history, was used by a closed source SGX driver. This was
a hack even then, and should not be needed anymore. So remove it.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>