staging: brcm80211: moved several README items to website

Intended audience for the README file are users of the driver.
Information only interesting to developers has been moved out of
the file and placed on the website:

http://linuxwireless.org/en/users/Drivers/brcm80211



Also, resolved bugs have been removed from the README.

Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>