staging: rtl8192u: ieee80211: Remove unused variables

The pointer *skb2 is declared 'globally' inside  ifdef NOT_YET.
It's used nowhere in the directory.
Another pointer *skb2 is declared 'locally', again inside another ifdef NOT_YET
in the function ieee80211_rx_frame_mgmt.
Hence, skb2 stays unused and has been removed.

This was done using Coccinelle:

@@ type T; identifier i; constant c; @@
-T i;
<... when != i
-i = c;
...>

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>