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

This reverts commit 0ba485f9 from
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: Iaa077692eb4daed68ecca85aab3be4106d04bc12
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>