Staging: xgifb: Remove unused functions

Earlier patch removed code that never got executed because it depended on
XGIfb_accel variable value to de distinct than 0. But this variable is
always 0 in current driver.

That dead code used a set of functions that not remains unused.

This patch removes these unused functions.

Signed-off-by: Javier Martinez Canillas <martinez.javier@gmail.com>
Acked-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>