AMDGPU: Fix asan errors when folding operands

This was failing when trying to fold immediates into operand 1 of a
phi, which only has one statically known operand.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289337 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed