[IA64] end of kernel 'data' is at _end, not _edata

/proc/iomem describes a block of memory as "Kernel data",
but the end address is derived from "_edata".  The kernel
actually has many other sections beyond _edata.  Get the
real end address from _end.

Acked-by: Khalid Aziz <khalid_aziz@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>