[IA64] Wrong args to memset in efi_gettimeofday()

Not sizeof(ptr) ... we meant to say sizeof(*ptr).

Also moved the memset to the error path (the normal path overwrites
every field in the structure anyway) -Tony

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>