Initialize RelativeRel for AMDGPU.
Initialize RelativeRel for AMDGPU.

Target->RelativeRel is used for all platforms, but AMDGPU did
not send that member.

Fixes bug 30227 - RelativeRel is used, but not initialized for AMDGPU.

Differential Revision: https://reviews.llvm.org/D24100

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@280291 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld