ia64: Fix some warnings introduced in merge window

Fix

  arch/ia64/kernel/irq_ia64.c:586:1: warning: no return statement in function returning non-void [-Wreturn-type]
  arch/ia64/mm/contig.c:111:6: warning: unused variable 'rc' [-Wunused-variable]
  arch/ia64/mm/discontig.c:189:39: warning: unused variable 'rc' [-Wunused-variable]

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>