AMDGPU/GFX10: Support DLC bit in llvm.amdgcn.s.buffer.load intrinsic

Summary: Change-Id: Ie4c971462a7749740938c687144e77441dac2539

Reviewers: rampitec, arsenm

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62486

Change-Id: Iae59523edd75c74918d2118df6571a7b671717a0
llvm-svn: 363514