Bluetooth: controller: llcp: update rx parameters upon receipt of PDU

According to specification, when executing a remote procedure the
rx parameters used need to be updated when the REQ from the peer
is received. Currently this is done only when an ACK is
received on the RSP PDU send out.
This commit updates the RX parameters upon receipt of the REQ PDU

Signed-off-by: Andries Kruithof <andries.kruithof@nordicsemi.no>