parisc: initialize unwinder much earlier

The unwinder was being initialized way too late to be any use
debugging early boot crashes. Instead of relying on module_init
initcalls to initialize it, let's do it explicitly as early as
we can.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>