[RFC 0/3] MIPS: add pre-bootloader (pbl) image support

[Antony Pavlov]

This patch series is based on ARM pbl support and allows
creating a pre-bootloader binary for compressed image.

TODO:
 * add lowlevel init;
 * current MIPS pbl run only on qemu-malta; make it work
on other boards (e.g. add mmc/nand boot support on Ingenic SOCs).

[RFC 1/3] MIPS: add pre-bootloader (pbl) image support
[RFC 2/3] MIPS: boot: realize _start in C
[RFC 3/3] MIPS: qemu-malta_defconfig: use pbl