Make it possible to use __start_notes and __stop_notes without getting a GPREL
overflow error from the FRV linker.

Small variables that would otherwise be in .data or .bss may, depending on the
arch, be placed in special sections (.sdata or .sbss) that permit single
instruction references on fixed instruction width machines.

__start_notes and __stop_notes aren't really char variables, and certainly
don't refer to data in .data or .bss.  Making them type "void" fools the
compiler into not assuming anything about them.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>