zd1211rw: collect driver settings and add function to restore theim

We need HW hard reset later in patchset to reset device after TX-stall.
Collect all settings that we have set to driver for later reset and
add restore function.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>