bluetooth: controller: Disable Coded PHY by default.

Coded PHY is only enabled by default if the application is using
BT_HCI_RAW.

Coded PHY is not needed in most applications.
By disabling Coded PHY, most applications will:

* Get smaller in terms of flash and ram usage
* Not get vurnerable to devices trying to switch to Coded and
  thereby increasing power consumption.

Signed-off-by: Rubin Gerritsen <rubin.gerritsen@nordicsemi.no>