This revision implements ubldr support for MIPS.
A lot of it just mimics the ARM support for ubldr, basically the biggest change is in the start.S file.
Apart from that, several Makefiles in sys/boot were not including the bsd.stand.mk, which prevented proper build for MIPS targets (due to some things compiled as PIC and others - as non-PIC). These Makefiles now include bsd.stand.mk and things build fine for MIPS (everything is build as non-PIC).
Currently the self relocation feature does not work and is disabled by default. I am not certain if this will be useful to pursue in the future, but I've left the relevant parts of code in case we want to do it some day.
I've used the head version of U-Boot and modified it to support the FreeBSD API for MIPS architectures. I've submitted the patch to U-Boot as well:
The corresponding U-Boot patch was applied as of commit 7c60423106bebafedbdd9879d84d105b3fb03930: