AMDGPU/GlobalISel: Basic legalize rules for G_FSHR

Only handles easy 32-bit cases.
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 51eec30..454a63e 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -3276,6 +3276,8 @@
   case G_FMAXNUM_IEEE:
   case G_FMINIMUM:
   case G_FMAXIMUM:
+  case G_FSHL:
+  case G_FSHR:
     return fewerElementsVectorBasic(MI, TypeIdx, NarrowTy);
   case G_SHL:
   case G_LSHR: