Add RMT receiver functions

[SzigetiJ]

Currently, the only function at the RX side of RMT is rmt_start_rx(ERmtChannel eChannel, bool bMemWrRst).
What is missing:

• Support read from RMT RAM when
  • multiple blocks are assigned to a channel,
  • wrap-around is enabled;
• Add current rx mem idx / rx wrapped / rx state attributes to SRmtStatusReg.

Also, provide a dummy example (connect RMT TX output signal to RMT RX input).