Bluetooth: Controller: Add missing check for Coded PHY support

Add missing check for Coded PHY support when creating
extended advertising set.

Added a fallback in Controller for upper layers requesting
Coded PHY while Controller is implemented without Coded PHY.
In this case, 1M PHY will be used in extended advertising
for testing purposes.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>