staging: rtl8192e: rtllib_tx: Make functions static

Make as many functions as possible static in rtllib_tx.c.

The following functions were affected:
- rtllib_xmit_inter
- rtllib_query_seqnum
- rtllib_put_snap

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>