AMDGPU: Use an ABS32_LO relocation for SCRATCH_RSRC_DWORD1

Summary:
Using HI here makes no logical sense, since the dword is only
32 bits to begin with.

Current Mesa master does not look at the relocation type at all,
so this change is fine. Future Mesa will rely on this, however.

Change-Id: I91085707834c4ac0370926602b93c94b90e44cb1

Reviewers: arsenm, rampitec, mareko

Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D55369

llvm-svn: 349620