Bluetooth: Change remote version event from prio to normal event type

This commit reverts the change that moved the remote version event from
a priority event to a normal event. This is done because the strategy
for using this event has been changed and will be used with a callback
instead of a semaphore that could be locked from the RX thread.

This commit retains the infrastructure that was added in the controller
so that moving events to priority processing is still possible.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>