Bluetooth: Controller: Update BT_CTLR_ADV_EXT_RX_CNT for ea and df

We need more RX nodes when scanning either extended/periodic advertising
trains and CTE samples so pudate those values based on observer and DF
features enabled.

The number of nodes for non-DF allows to scan complete chain for each
aux scan set (assuming max data length and optimal fragmentation by
advertiser), for DF it allows to scan max possible PDUs and CTE samples.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>