staging: r8821ae: Fix build problems

As initially introduced, this driver failed to build in the linux-next
tree due to changes coming from newer developments arising in the
wireless trees. This patch removes incompatible code and provides
definitions for symbols that have been removed from mac80211.

In addition, several warnings were fixed.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>