powerpc: Merge asm-ppc/kexec.h and asm-ppc64/kexec.h

Merge include/asm-ppc/kexec.h and include/asm-ppc64/kexec.h.

The only thing that's really changed is that we now allocate crash_notes
properly on PPC32. It's address is exported via sysfs, so it's not correct
for it to be a pointer.

I've also removed some of the "we don't use this" comments, because they're
wrong (or perhaps were referring only to arch code).

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

arch/ppc/kernel/machine_kexec.c

@@ -32,7 +32,7 @@ const extern unsigned int relocate_new_kernel_size;
  * Provide a dummy crash_notes definition while crash dump arrives to ppc.
  * This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
  */
-void *crash_notes = NULL;
+note_buf_t crash_notes[NR_CPUS];
 
 void machine_shutdown(void)
 {