[PATCH] powerpc: Fix kdump copy regs and dynamic allocate per-cpu crash notes

- This contains the arch specific changes for the following the
kdump generic fixes which were already accepted in the upstream.
       .   Capturing CPU registers (for the case of 'panic' and invoking
the dump using 'sysrq-trigger') from a function (stack frame) which will
be not be available during the kdump boot. Hence, might result in
invalid stack trace.
       .   Dynamically allocating per cpu ELF notes section instead of
statically for NR_CPUS.

- Fix the compiler warning in prom_init.c.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>