[AArch64][GISel] Additional FPExt vector lowering

Similar to D155311, this adds lowering for more vector cases for FPExt

Differential Revision: https://reviews.llvm.org/D155601
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index af5ff9e..f0da0d8 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -4950,7 +4950,8 @@
     Observer.changedInstr(MI);
     return Legalized;
   }
-  case TargetOpcode::G_FPTRUNC: {
+  case TargetOpcode::G_FPTRUNC:
+  case TargetOpcode::G_FPEXT: {
     if (TypeIdx != 0)
       return UnableToLegalize;
     Observer.changingInstr(MI);