Revert "mm/hugetlb: fix missing hugetlb_lock for resv uncharge"

This reverts commit 4c806333 which is
commit b76b4690 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I134d1423c7d4a26b29dd043c5b5dae84d0e64fa5
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>