elf core dump: notes reorg

This pulls out the code for writing the notes segment of an ELF core dump
into separate functions.  This cleanly isolates into one cluster of
functions everything that deals with the note formats and the hooks into
arch code to fill them.  The top-level elf_core_dump function itself now
deals purely with the generic ELF format and the memory segments.

This only moves code around into functions that can be inlined away.
It should not change any behavior at all.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>