ARM: 9161/1: mm: mark private VM_FAULT_X defines as vm_fault_t

This fixes several sparse warnings for fault.c:

arch/arm/mm/fault.c:210:24: sparse:     expected restricted vm_fault_t
arch/arm/mm/fault.c:210:24: sparse:     got int
...
arch/arm/mm/fault.c:345:24: sparse: sparse: restricted vm_fault_t degrades to integer

Reported-by: kernel test robot <lkp@intel.com>
Fixes: caed89da ("ARM: 9128/1: mm: Refactor the __do_page_fault()")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>