tests/bluetooth/tester: Fix possible buffer overflow
tests/bluetooth/tester: Fix possible buffer overflow

Make sure we have enough space for notification data.

Signed-off-by: Szymon Janc <db186c297188f7acbbdc9bbd6aff2f45665bb42d@codecoup.pl>

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