staging: r8712u: Add missing initialization and remove configuration parameter CONFIG_R8712_AP

When this driver was upgraded to the vendor 20100831 version in
commit 93c55dda et al,, one listhead initialization was missed.
This broke complete operation of the driver whenever AP mode was
enabled. This fixes https://bugs.archlinux.org/task/27996

.

The configuration parameter R8712_AP is misleading as the driver cannot
function as an AP without a heavily hacked version of hostapd. Thus, it
makes sense to remove the parameter; however the code and data configured
for the option is left in.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>