ia64: remove duplicate declarations of __per_cpu_start[] and __per_cpu_end[]

They're already provided by <asm/sections.h>.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>