um: uml_setup_stubs': warning: unused variable 'pages'

Fix the following gcc complain
arch/um/kernel/skas/mmu.c: In function 'uml_setup_stubs':
arch/um/kernel/skas/mmu.c:106:16: warning: unused variable 'pages' [-Wunused-variable]

Signed-Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Richard Weinberger <richard@nod.at>