ISDN: eicon: silence misleading array-bounds warning

With some gcc versions, we get a warning about the eicon driver,
and that currently shows up as the only remaining warning in one
of the build bots:

In file included from ../drivers/isdn/hardware/eicon/message.c:30:0:
eicon/message.c: In function 'mixer_notify_update':
eicon/platform.h:333:18: warning: array subscript is above array bounds [-Warray-bounds]

The code is easily changed to open-code the unusual PUT_WORD() line
causing this to avoid the warning.

Cc: stable@vger.kernel.org
Link: http://arm-soc.lixom.net/buildlogs/stable-rc/v4.4.45/


Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>