dev-manual, mega-manual: Updated kernel-overview-2-generic.png file.

There was a sample string in this tree that ended in "ro" when it
should have been "r0" (as in release 0). Anytime you update a figure,
the modified file must go in both the "figures" directory of both
the manual (dev-manual in this case) and in the mega-manual.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
(From yocto-docs rev: 8e75cc23fbf03f355fade416a12b7c8fe1e656a5)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>