Returns the AFE conversion data corresponding to channel CSEL (configured in the AFEC Channel Selection Register).
At the end of a conversion, the converted data is loaded into one of the
12 internal registers (one for each channel) and remains in
this internal register until a new conversion is completed on the same channel index.
The AFEC_CDR together with AFEC_CSELR allows to multiplex all the internal channel
data registers.
The data carried on AFEC_CDR is valid only if AFEC_CHSR.CHx bit is set (where x = AFEC_CSELR.CSEL field value).
