linux-kexecboot: remove all, now we use linux-yocto-tiny-kexecboot

* The linux-yocto-tiny-kexecboot recipe can be extended and support
* more devices migrating the patches and renaming the defconfig as
* done for Sharp Zaurus devices.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>