[IA64] Shrink shadow_flush_counts to a short array to save 8k of per_cpu area.

Making allmodconfig will break the current build.  This patch shrinks
the per_cpu__shadow_flush_counts from 16k to 8k which frees enough space
to allow allmodconfig to successfully complete.

Fixes http://bugzilla.kernel.org/show_bug.cgi?id=11338

Signed-off-by: Robin Holt <holt@sgi.com>
Acked-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>