This commit adds support for dfu targets for cmake2. The following
changes have been made:
- Adds a new tools/cmakev2/dfu.cmake file on similar lines as the
tools/cmake/dfu.cmake file.
- Adds the idf_create_dfu() function to create the dfu targets. This
function now takes the executable as an argument thus allowing the dfu
target to be created per-executable.
- idf_project_default() is updated to create the dfu target.
Sudeep Mohanty