[IA64] Minor cleanups - remove unnecessary function prototype in iosapic.h

[IA64] Minor cleanups - remove unnecessary function prototype in iosapic.h

The function prototypes for iosapic_enable_intr() and
iosapic_pci_fixup() in include/asm-ia64/iosapic.h are no longer
needed. This patch removes them. The original patch has been posted by
Satoru Takeuchi.

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>