Now that sys_ipc has been removed from xtensa, asm/ipc.h is no longer
needed for that architecture.  Not tested, but obviously correct.  This
file is included only from arch code and this patch also removes the only
inclusion.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>