kernel-artifact-names.bbclass: Add 2 more variables to make it easier to change all names with one variable
* some people don't like the ${MACHINE} in the symlink, because now the DEPLOYDIR already
contains ${MACHINE} subdirectory, add KERNEL_ARTIFACT_LINK_NAME variable to change it
in one place without the need to list all variables for various artifacts
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
