default-distrovars.inc: add debuginfod to default DISTRO_FEATURES

Obtaining debug information by having it served automatically via http
is far more pleasant than messing about with debugfs and gdbserver or
transferring and installing -dbg packages by hand.

I believe we should follow the desktop distros and have it enabled
out of the box. Please see the following commit for the description
of how it works.

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>