[libunwind][ARM] Fix types in _Unwind_VRS_Get.

This is a small fix for https://reviews.llvm.org/D64996. The types of
w0 and w1 in _Unwind_VRS_Get must be uint64_t, not uint32_t.

Committing as obvious.

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@366701 91177308-0d34-0410-b5e6-96231b3b80d8