s390/mm,fault: remove VM_FAULT_PFAULT

s390/mm,fault: remove VM_FAULT_PFAULT

Handling of VM_FAULT_PFAULT and VM_FAULT_BADCONTEXT is nearly identical;
the only difference is within do_no_context() where however the fault_type
(KERNEL_FAULT vs GMAP_FAULT) makes sure that both types will be handled
differently.

Therefore it is possible to get rid of VM_FAULT_PFAULT and use
VM_FAULT_BADCONTEXT instead.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>