Remove useless wrappers of asm-generic/ipc.h

mn10300 has a header (in its include/asm directory) that is a thin
wrapper around asm-generic/ipc.h. This wrapper is useless, since that
header doesn't exist. It is also unused (no file includes asm/ipc.h).

hexagon and tile generate similar headers at build time (using a
generic-y entry in include/asm/Kbuild). These generated headers are
useless and unused too.

Remove this header and these generic-y entries.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Richard Kuo <rkuo@codeaurora.org>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: David Howells <dhowells@redhat.com> [MN10300]
Signed-off-by: Michal Marek <mmarek@suse.cz>