pch_phub: Improve ADE(Address Decode Enable) control

Currently, external ROM access is enabled/disabled in probe()/remove().
So, when a buggy software access unanticipated memory area,
in case of enabling this ADE bit,
external ROM memory area can be broken.

This patch enables the ADE bit only accessing external ROM area.

Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Cc: Masayuki Ohtak <masa-korg@dsn.okisemi.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Denis Turischev <denis@compulab.co.il>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>