Bluetooth: ISO: Fix build on native_posix_64 with debug
Bluetooth: ISO: Fix build on native_posix_64 with debug

On native_posix_64 we get the following compile error in CI:

error: format %u expects argument of type unsigned int

Fix by using %zu instead of %u as type is of size_t.

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

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