bluetooth/tester: give data buffer for each L2CAP channel
bluetooth/tester: give data buffer for each L2CAP channel

L2CAP channels are allocating buffers from common data_pool. For that
pool buffer count was hard-coded as 1. This count should be set to value
CHANNELS, allowing each channel to allocate buffer for incoming
data. Without this change, execution would stuck at l2cap_chan_le_recv()
as we give net_buf_alloc() in alloc_buf_cb() no timeout.

Signed-off-by: Krzysztof Kopyściński <48568cfaa134e87f8b8a21a5eb21757e127be81c@codecoup.pl>

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