USB gadget support is missing in db410c BSP (both upstream and Qcomlt-4.14 tree), so no ADB or any other Android gadget is supported.
There are, however, few out of tree patches floating around which can get USB gadgets working. Cherry pick top 3 patches from https://android-git.linaro.org/kernel/linaro-android.git/log/?h=test/db410c-llct and rebuild the your kernel for ADB support. These patches are incomplete though and user need to manually switch between USB host and gadget mode from commandline.
Run following commands to switch between Gadget and Host modes:
echo host > /sys/bus/platform/devices/ci_hdrc.0/role
echo gadget > /sys/bus/platform/devices/ci_hdrc.0/role
Default mode is gadget.