Merge branch '2022-01-24-assorted-fixes-and-updates'

- Assorted dumpimage/mkimage fixes, allow setting the signature
  algorithm on the command line with mkimage
- Bugfix to the misc uclass, CONFIG_MP / CMD_MP Kconfig logic improved,
  updated Xen platform MAINTAINERS entry and fixed vexpress_aemv8a_semi
  booting.