sparc64: update pmdp_invalidate() to return old pmd value

It's required to avoid losing dirty and accessed bits.

[akpm@linux-foundation.org: add a `do' to the do-while loop]
Link: http://lkml.kernel.org/r/20171213105756.69879-9-kirill.shutemov@linux.intel.com


Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>