[PATCH] wireless: WE-20 compatibility for ESSID and NICKN ioctls

WE-21 changed the ABI for the SIOC[SG]IW{ESSID,NICKN} ioctls by dropping
NULL termination.  This patch adds compatibility code so that WE-21 can
work properly with WE-20 (and older) tools.

Signed-off-by: John W. Linville <linville@tuxdriver.com>