staging: r8188eu: remove rtw_hal_xmitframe_enqueue function

Remove rtw_hal_xmitframe_enqueue from hal/hal_intf.c and its one
caller from core/rtw_recv.c, and remove its declaration from
include/hal_intf.h as well. This is just a wrapper function that calls
the function pointer hal_xmitframe_enqueue in struct hal_ops if it
is set, which it never is.

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210906010106.898-10-phil@philpotter.co.uk


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