staging: rtl8723bs: Replace function rtw_free_network_queue()

Remove function rtw_free_network_queue as all it does is call
_rtw_free_network_queue.
Rename _rtw_free_network_queue to rtw_free_network_queue to maintain
compatibility with call sites.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>