staging: r8188eu: remove unused prototypes from recv_osdep.h

The function prototypes rtw_recv_returnpacket(), rtw_init_recv_priv()
and rtw_free_recv_priv() are not used. Remove them.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220911174933.3784-3-straube.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>