* grub-core/kern/efi/efi.c (grub_rtc_get_time_ms) [__ia64__]: Remove on
ia64.
(grub_get_rtc) [__ia64__]: Likewise.
* grub-core/kern/ia64/efi/init.c (divisor): New variable.
(get_itc): New function.
(grub_rtc_get_time_ms): Likewise.
(grub_machine_init): Calibrate ITC.
* include/grub/efi/time.h (grub_get_rtc), (GRUB_TICKS_PER_SECOND):
Keep only on non-ia64. Don't export since it's broken and used only
if TSC is unavailable.
