staging: r8188eu: remove rtw_usb_bulk_msg() macro

No one is using this wrapper macro, so just remove it as it is
pointless.

Link: https://lore.kernel.org/r/20210730092417.1014392-11-gregkh@linuxfoundation.org


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