Implement support for membooting pnor images

[amboar]

mboxd (soon to be renamed to hiomapd) recently added support for booting from a pnor file placed e.g. in /tmp on the BMC. This reduces the turn-around time for testing images by avoiding the erase/write cycles required to get the image onto the host flash device. Support memboot if the functionality is available.

[amboar]

I'll take this one if someone can assign it to me.

[oohal]

ping?

[amboar]

Unfortunately it's fallen to the bottom of the todo list for the moment, would be great if someone else could pick it up instead.