We now use MIPS_CMDLINE_DTB_EXTEND for all boot varieties
(tftpboot, flash boot, kexec) with the addition of
MIPS_BOOTLOADER_CMDLINE_REQUIRE_COOKIE - local patch -
so that the bootloader args are ignored unless they
contain the string "liminix"
This allows booting a new image from a running OS, creating a
phram mtd for the root squashfs
* enable CONFIG_KEXEC
* add modules/kexecboot
* patch kexec-tools to add --map-file option for the squashfs
* patch kernel kexec code to call new kernel with DTB
