boards: Select SDC for nRF54LM20A board

Commit b828ce7 enabled bt_hci_sdc and disabled
bt_hci_controller, but bt_hci_controller is still the
default controller. This commit also selects
bt_hci_sdc as default controller.

Signed-off-by: Dominik Kilian <[email protected]>

Author: doki-nordic

boards/nordic/nrf54lm20apdk/nrf54lm20apdk_nrf54lm20a_cpuapp.dts

@@ -15,6 +15,7 @@
 	chosen {
 		zephyr,code-partition = &slot0_partition;
 		zephyr,sram = &cpuapp_sram;
+		zephyr,bt-hci = &bt_hci_sdc;
 	};
 };