staging: r8188eu: make rtl8188eu_{init,free}_recv_priv() static

staging: r8188eu: make rtl8188eu_{init,free}_recv_priv() static

The functions rtl8188eu_init_recv_priv() and rtl8188eu_free_recv_priv()
are only used in rtw_recv.c. Make them static and remove the now empty
file rtl8188eu_recv.c.

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/20220804105532.7532-3-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>