Bluetooth: radio: move radio_df_cte_inline_set_enabled to radio.c

To enable runtime parsing of PDU to find CTEInfo field CTEINLINE mode
has to be enabled. Thanks to that it is possible to verify if the PDU
has allowed CTE type e.g. for periodic advertising synchornization.
To run CTEInfo parsing other parametrers of CTEINLINE are not relevant.
If Radio is set to disable after PDU END event the CTE sampling
will not be processed.

The commit moves the radio_df_cte_inline_set_enable function to make
it accessible even the direction finding features are disabled.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>