[ZD1211RW]: Removed zd_util.c and zd_util.h

The kernel now provides a generic hexdump implementation should we need
it again, so we can remove it from zd1211rw. After removing that, only
one single-user function is left in zd_util. Move that to zd_mac and
remove zd_util.

Signed-off-by: Ulrich Kunitz <kune@deine-taler.de>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>