Revert "serial: max310x: make accessing revision id interface-agnostic"

This reverts commit 8082cc99 which is
commit b3883ab5 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: Ibe6d74a96dd665e39c32618207d2df190e769c67
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>