[IA64] fix compilation error caused by 19046:ecf603780f56

[IA64] fix compilation error caused by 19046:ecf603780f56

This patch fixes the following compilation error adjusting
function prototypes.

> xc_core_ia64.c:176: error: conflicting types for
  'xc_core_arch_memory_map_get'
> xc_core.h:141: error: previous declaration of
  'xc_core_arch_memory_map_get' was here
> xc_core_ia64.c:241: error: conflicting types for
  'xc_core_arch_map_p2m'
> xc_core.h:144: error: previous declaration of 'xc_core_arch_map_p2m'
  was here

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>