Bluetooth: iso: Fix ISO data path setup

This patch fixes ISO data path setup that shall be done for enabled
directions only and removes usage of Path ID = 0xFF which is RFU value.

As per Core 5.3 Vol 4, Part E, 7.8.109
"If the Host attempts to set an output data path using a connection handle
that is for an Isochronous Broadcaster, for an input data path on a
Synchronized Receiver, or for a data path for the direction on a
unidirectional CIS where BN is set to 0, the Controller shall return the
error code Command Disallowed (0x0C)."

Fixes: #43190
Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>