[AMDGPU] Remove FeatureVGPRSpilling

This feature is only relevant to shaders, and is no longer used. When disabled,
lowering of reserved registers for shaders causes a compiler crash.

Remove the feature and add a test for compilation of shaders at OptNone.

Differential Revision: https://reviews.llvm.org/D53829

llvm-svn: 345763
diff --git a/llvm/test/CodeGen/AMDGPU/local-stack-slot-offset.ll b/llvm/test/CodeGen/AMDGPU/local-stack-slot-offset.ll
index 928eeca..790715c 100644
--- a/llvm/test/CodeGen/AMDGPU/local-stack-slot-offset.ll
+++ b/llvm/test/CodeGen/AMDGPU/local-stack-slot-offset.ll
@@ -1,5 +1,5 @@
-;RUN: llc < %s -march=amdgcn -mcpu=verde -mattr=+vgpr-spilling -mattr=-promote-alloca -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
-;RUN: llc < %s -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -mattr=+vgpr-spilling -mattr=-promote-alloca -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
+;RUN: llc < %s -march=amdgcn -mcpu=verde -mattr=-promote-alloca -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
+;RUN: llc < %s -march=amdgcn -mcpu=tonga -mattr=-flat-for-global -mattr=-promote-alloca -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
 
 ; Allocate two stack slots of 2052 bytes each requiring a total of 4104 bytes.
 ; Extracting the last element of each does not fit into the offset field of