Staging: vt6655: Fix Sparse Warning for Static Declarations in tkip.c

This patch fixes the Sparse Warning "symbol was
not declared. Should it be static?" in tkip.c

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Reviewed-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>