[AMDGPU][MC][GFX8+][DISASSEMBLER] Corrected 1/2pi value for 64-bit operands

See bug 39332: https://bugs.llvm.org/show_bug.cgi?id=39332

Reviewers: artem.tamazov, arsenm

Differential Revision: https://reviews.llvm.org/D56794

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351555 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed