staging: r8188eu: remove rf_type from rtw_mcs_rate()

rf_type is always RF_1T1R. Remove it from rtw_mcs_rate() and remove
related dead code.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20211118215052.5215-1-straube.linux@gmail.com


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