Bluetooth: Controller: df: make radio_df_vendor_hal.h compile in always

The header file radio_df_vendor_hal.h was conditionally copiled in.
There were a dependency on a CONFIG_BT_CTRL_DR. The dependency is
removed because radio_df_vendor_hal.h and radio_df.h hasn't got any
DF related type dependencies. What more it allows to use IS_ENABLED
for code that uses types and functions defined in radio_df.h.

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