Bluetooth: hci_core: Exclude conn creation related code for non-central
Bluetooth: hci_core: Exclude conn creation related code for non-central

Don't build the code that is related to central role if the target
does not support connection creation.
This helps to reduce the application image size that implement
either Observer, Peripheral or Broadcaster role.

Note:
BT_CENTRAL implies BT_CONN and BT_OBSERVER

Signed-off-by: Mariusz Skamra <c73850bd0bf85e95dce44c2ce1418ca55c1b6c5d@codecoup.pl>

punitvara/zephyr,punitvara/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,ldts/zephyr,kraj/zephyr,punitvara/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,Vudentz/zephyr,explora26/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,ldts/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,explora26/zephyr,ldts/zephyr,punitvara/zephyr,finikorg/zephyr,finikorg/zephyr,explora26/zephyr,Vudentz/zephyr,punitvara/zephyr,galak/zephyr,explora26/zephyr,galak/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,finikorg/zephyr,kraj/zephyr