ARM: fix warnings introduced by previous patch

869486d5f51 (ARM: 7646/1: mm: use static_vm for managing static mapped
areas) introduced new warnings:

arch/arm/mm/mmu.c: In function 'pci_reserve_io':
arch/arm/mm/mmu.c:888:16: warning: unused variable 'addr'
arch/arm/mm/mmu.c:887:20: warning: unused variable 'vm'

because it failed to delete the two local variables it no longer used.
Fix this.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>