[RISCV][GISel] Remove legalIf from G_ZEXT, G_SEXT, G_ANYEXT.

[craig.topper]

Summary

I think after making G_SEXT_INREG legal this isn't needed. At the
very least its not tested anymore.

llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp

getActionDefinitionsBuilder(
       .widenScalarToNextPow2(0);
 
   getActionDefinitionsBuilder({G_ASHR, G_LSHR, G_SHL})
       .legalFor({{XLenLLT, XLenLLT}})
       .widenScalarToNextPow2(0)
       .clampScalar(1, XLenLLT, XLenLLT)
       .clampScalar(0, XLenLLT, XLenLLT);
 
-  // Extensions
-  auto ExtLegalFunc = [=](const LegalityQuery &Query) {
-    unsigned DstSize = Query.Types[0].getSizeInBits();
-
-    // Make sure that we have something that will fit in a register, and
-    // make sure it's a power of 2.
-    if (DstSize < 8 || DstSize > XLen || !isPowerOf2_32(DstSize))
-      return false;
-
-    const LLT SrcTy = Query.Types[1];
-
-    // Make sure we fit in a register otherwise. Don't bother checking that
-    // the source type is below 2 * XLen bits. We shouldn't be allowing anything
-    // through which is wider than the destination in the first place.
-    unsigned SrcSize = SrcTy.getSizeInBits();
-    if (SrcSize < 8 || !isPowerOf2_32(SrcSize))
-      return false;
-
-    return true;
-  };
   getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT})
-      .legalIf(ExtLegalFunc)
-      .clampScalar(0, XLenLLT, XLenLLT);
+      .maxScalar(0, XLenLLT);
 
   getActionDefinitionsBuilder(G_SEXT_INREG)
       .legalFor({XLenLLT})
       .maxScalar(0, XLenLLT)
       .lower();
 
   // Merge/Unmerge
   for (unsigned Op : {G_MERGE_VALUES, G_UNMERGE_VALUES}) {