x86_64, entry: Merge most 64-bit asm entry macros

x86_64, entry: Merge most 64-bit asm entry macros

I haven't touched the device interrupt code, which is different
enough that it's probably not worth merging, and I haven't done
anything about paranoidzeroentry_ist yet.

This appears to produce an entry_64.o file that differs only in the
debug info line numbers.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/e7a6acfb130471700370e77af9e4b4b6ed46f5ef.1400709717.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>