ANDROID: ashmem: fix up vm_flags direct access which is not allowed anymore

Commit 1c71222 ("mm: replace vma->vm_flags direct modifications
with modifier calls") removed the ability to directly access vm_flags, but
provided wrapper functions to do the task instead.  Use vm_flags_clear()
to fix the build breakage in the ashmem code because of this change.

Fixes: 1c71222 ("mm: replace vma->vm_flags direct modifications with modifier calls")
Cc: Suren Baghdasaryan <surenb@google.com>
Change-Id: I865469c1eacd8d037eaaa85eca65e54f717e8706
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
(cherry picked from commit 78ffde117c5448314e99fdc58041712bcb065c9b)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

Author: gregkh

drivers/staging/android/ashmem.c

@@ -401,7 +401,7 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
 		ret = -EPERM;
 		goto out;
 	}
-	vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
+	vm_flags_clear(vma, calc_vm_may_flags(~asma->prot_mask));
 
 	if (!asma->file) {
 		char *name = ASHMEM_NAME_DEF;