x86_64, entry: Merge paranoidzeroentry_ist into idtentry

One more specialized entry function is now gone.  Again, this seems
to only change line numbers in entry_64.o.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/f54854f07ff3be8162b166124dbead23feeefe10.1400709717.git.luto@amacapital.net


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>