staging: r8188eu: move rtw_os_xmit_complete() to rtw_xmit.c

Move the function rtw_os_xmit_complete() from the os_dep/xmit_linux.c
to core/rtw_xmit.c. The goal is to get rid of os_dep/xmit_linux.c in
follow up patches.

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/20220820181623.12497-15-straube.linux@gmail.com


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