[PATCH] zd1211rw: Reject AL2230S devices

zd1211rw currently detects AL2230S-based devices as AL2230, and hence
programs the RF incorrectly. Transmit silently fails on this
misconfiguration.

After this patch, AL2230S devices are rejected with an error message, to
avoid any confusion with an apparent driver bug.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>