Bluetooth: ISO: Add iso channel state check for unbind
Bluetooth: ISO: Add iso channel state check for unbind

A channel should only be allowed to unbind when in
the BT_ISO_BOUND state. If it is in a disconnected state,
then it the function would have meaning. If it is a connected
state, unbinding it would generate an error when removing
the CIG, which would fail silently.

Signed-off-by: Emil Gydesen <a20314356615223738233ab4c4eb1cd8cd4146fa@nordicsemi.no>

galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr