Currently we have call parse_early_param() earliyish, but not really very
early. In particular, it's not early enough to do things like mem=x or
crashkernel=blah, which is annoying.

So do it earlier. I've checked all the early param handlers, and none of them
look like they should have any trouble with this. I haven't tested the
booke_wdt ones though.

On 32-bit we were doing the CONFIG_CMDLINE logic twice, so don't.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>