kexecboot_cfg: add missing default OE icon.xpm

* while there do minor cleanings wrt DISTRO vars:
* remove ${@base_conditional('DISTRO_TYPE',...
* fix label of second kernel stanza
* bump PR

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