Staging: xgifb: use %lx instead of %x in printk format

This fixes compiler warning  format '%x' expects type 'unsigned int',
but argument 2 has type 'long unsigned int'

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Cc: Arnaud Patard <apatard@mandriva.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>