Revert "fs: Convert to bdev_open_by_dev()"

This reverts commit 4365d0d6 which is
commit f4a48bc3 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: I36bf7e4279a05eb0028ea4da17a2cb735de04bdc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>