board: dragonboard410c: import board code from mach-snapdragon

Some of the db410c board support code was written to be generic and
placed in mach-snapdragon. However, as the db410c is the only board
using this, move the code out of mach-snapdragon. This makes is more
obvious what code is relevant for which targets and helps tidy things up
a little more.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org> #qcs404
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>