tools/testing/vma: add missing stub

vm_flags_reset() is not available in the userland VMA tests, so add a stub
which const-casts vma->vm_flags and avoids the upcoming removal of the
vma->__vm_flags field.

Link: https://lkml.kernel.org/r/4aff8bf7-d367-4ba3-90ad-13eef7a063fa@lucifer.local
Fixes: c5c67c1 ("tools/testing/vma: eliminate dependency on vma->__vm_flags")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ljskernel

tools/testing/vma/vma_internal.h

@@ -1549,4 +1549,11 @@ static inline int do_munmap(struct mm_struct *, unsigned long, size_t,
 	return 0;
 }
 
+static inline void vm_flags_reset(struct vm_area_struct *vma, vm_flags_t flags)
+{
+	vm_flags_t *dst = (vm_flags_t *)(&vma->vm_flags);
+
+	*dst = flags;
+}
+
 #endif	/* __MM_VMA_INTERNAL_H */