staging: ks7010: add driver from Nanonote extra-repository

See the TODO for details where this driver came from. Only a few minor
changes were made to make the driver suitable for staging:

* updated Kconfig help text and dependencies
* added TODO
* removed two __DATE__ and __TIME__ printouts to allow reproducible builds
* added to staging main Kconfig + Makefile

Tested on a Renesas Salvator-X board with a Spectec SDW-823 card. I
could connect to a WPA-protected network.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>