[IA64] Fix section conflict of ia64_mlogbuf_finish

Building with GCC 4.2, I get the following error:

  CC      arch/ia64/kernel/mca.o
arch/ia64/kernel/mca.c:275: error: __ksymtab_ia64_mlogbuf_finish causes a
section type conflict

This is because ia64_mlogbuf_finish is both declared static and exported.
Fix by removing the export (which is unneeded now).

Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>