i4l: silence compiler warnings for array access in Eicon DIVA ISDN driver

When compiling this driver, the compiler throws the following warnings:

drivers/isdn/hardware/eicon/message.c:8426: warning: array subscript is above array bounds
drivers/isdn/hardware/eicon/message.c:8427: warning: array subscript is above array bounds
drivers/isdn/hardware/eicon/message.c:8434: warning: array subscript is above array bounds
drivers/isdn/hardware/eicon/message.c:8435: warning: array subscript is above array bounds
drivers/isdn/hardware/eicon/message.c:8436: warning: array subscript is above array bounds
drivers/isdn/hardware/eicon/message.c:8447: warning: array subscript is above array bounds

This arises from the particular semantics the driver is using to write to
the nlc array (static byte[256]).  The array has a length in byte 0
followed by a T30_INFO struct starting at byte 1.

The T30_INFO struct has a number of variable length strings after the
station_id entry, which cannot be explicitly defined in the struct and the
driver accesses them with an array index to station_id beyond the length
of station_id.

This patch merely changes the semantics that the driver uses to access the
entries after the station_id entry to use the original 256 byte nlc array
taking the offset and length of the station_id entry to calculate where to
write in the array, thereby silencing the warning.

Signed-off-by: Ian Munsie <imunsie@au.ibm.com>
Cc: Armin Schindler <mac@melware.de>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Stoyan Gaydarov <sgayda2@uiuc.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>