Bluetooth: Controller: Fix BT_LL_SW_LLCP_LEGACY compile error

Fix compile error building application with
BT_LL_SW_LLCP_LEGACY. Request Peer SCA command is not
supported in legacy control procedure implementation.

Relates to commit 76439d0b ("Bluetooth: controller:
integrating SCA procedure and adding HCI API").

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