staging: brcm80211: replace macro BCM_MSG_IFNAME_MAX with IFNAMSIZ

In dhd.h the macro BCM_MSG_IFNAME_MAX was defined and used. As this
is used to carry the interface name we might as well use IFNAMSIZ
which results in the same size.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>