Fixes [YOCTO #4072]
Added a new description for the INITRAMFS_IMAGE variable. Also,
made a formatting fix to the INITRAMFS_IMAGE_BUNDLE variable.
(From yocto-docs rev: 87c5c0b1554233c3ce1c41291d852021ec62e0dc)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>