Staging: bcm: Remove null dereference from InterfaceWRM.

This patch removes a potential null dereference
from InterfaceMisc.c, function InterfaceWRM. This
error was reported by Smatch.

Signed-off-by: Kevin McKinney <klmckinney1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>