Although useful for me, loader.dump is not generally required so remove the
target for it.
Build 'jtagboot' and 'flashboot' without .elf names; also generate MD5s
that flashit would like to have handy.  For jtagboot, the output is ELF;
for flashboot, it's a memory image generated with objcopy.
In the BERI kernel boot code, extract 'boothowto' (which includes boot flags
such as '-s') and 'envp' from passed module data.  Booting to single-user
mode using boot flags now works.
Fix up parsing of boot2 device-name input: properly handle units in (some)
names, use the correct local variable.