staging: rtl8188eu: remove wrapper odm_SignalScaleMapping()

The function odm_SignalScaleMapping() is just a wrapper for
odm_SignalScaleMapping_92CSeries().

Rename odm_SignalScaleMapping_92CSeries() to odm_SignalScaleMapping()
and remove the wrapper.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>