Staging: xgifb: Remove unused spinlock conditional compilation logic

xgifb staging driver for XG20, XG21, XG40, XG42 frame buffer device
has a accelerator engine that never get used (XGIfb_accel is always 0).

Also the driver has a set of defines that hides the synchronization
mechanism used to access critical sections and a way to disable spinlocks
use at compile time.

In a earlier patch all the code that depends on the accelerator being active
was deleted because it was dead code. Since the only usage of this
synchronization defines were in that dead code, this patch removes all the
now unused spinlock conditional compilation logic.

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>