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"
* at the base address we were using, the filesystem was getting
corrupted presumably because the kernel unpacked into it
* leave a little more space between compressed kernel and
squashfs. this is probably ineffective but also harmless
