staging: rtl8723bs: Replace function odm_SignalScaleMapping()
Remove function odm_SignalScaleMapping as all it does is call
odm_SignalScaleMapping_92CSeries.
Rename odm_SignalScaleMapping_92CSeries to odm_SignalScaleMapping and
change its type from static to non-static to maintain compatibility with
call sites of odm_SignalScaleMapping.
Issue found with Coccinelle.