fix: 修改MMU模块的注释错误

修改los_arch_mmu.c中的page_idx 为scanIndex，修改pmm_alloc_page为LOS_PhysPageAlloc。

fix #I4KMMJ

Signed-off-by: kenneth <zhushangyuan@huawei.com>

kernel/base/vm/los_vm_fault.c

@@ -193,7 +193,7 @@ status_t OsDoCowFault(LosVmMapRegion *region, LosVmPgFault *vmPgFault)
 
     newPage = LOS_PhysPageAlloc();
     if (newPage == NULL) {
-        VM_ERR("pmm_alloc_page fail");
+        VM_ERR("LOS_PhysPageAlloc failed");
         ret = LOS_ERRNO_VM_NO_MEMORY;
         goto ERR_OUT;
     }