staging: r8188eu: remove xmit_osdep.h

staging: r8188eu: remove xmit_osdep.h

After previous cleanups the header xmit_osdep.h only contains some
structure forward declarations and extern declarations for some module
parameters. The forward declarations are not needed. We can make the
module parameters static in os_dep/os_intf.c and remove xmit_osdep.h.

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/20220820181623.12497-20-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>