modify page_fault_process()

- change its argument from 'struct process *'
                        to 'struct process_vm *'.
- change its name from 'page_fault_process()'
                    to 'page_fault_process_vm()'.
- allow to resolve a fault on the process_vm of another process.

kernel/include/process.h

@@ -450,7 +450,8 @@ struct vm_range *previous_process_memory_range(
 int extend_up_process_memory_range(struct process_vm *vm,
 		struct vm_range *range, uintptr_t newend);
 
-int page_fault_process(struct process *proc, void *fault_addr, uint64_t reason);
+int page_fault_process_vm(struct process_vm *fault_vm, void *fault_addr,
+		uint64_t reason);
 int remove_process_region(struct process *proc,
                           unsigned long start, unsigned long end);
 struct program_load_desc;