boards: kconfig: Disable QEMU icount when Bluetooth is enabled

Bluetooth interacts with real-world hardware and thus requires the QEMU
target to follow wall time, and not have a free running timer that is
much faster than actual wall time.

Diable the QEMU icount mechanism when Bluetooth is enabled.

Fixes #26242

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>