[COFF] Sort .pdata for arm64

This works for linking the output from the MSVC compiler.
The pdata entries for arm64 seem to be 8 bytes in the same
(or at least similar) form to arm.

Differential Revision: https://reviews.llvm.org/D41160

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@320676 91177308-0d34-0410-b5e6-96231b3b80d8