[mlir-tblgen] Fix bug in emitEnumDoc (#118131)

Fixes a crash (assertion failure) in `mlir-tblgen -emit-enum-doc` caused
by calling `EnumAttr()` for the wrong type of `Record *`: `EnumAttr`
rather than `EnumAttrInfo` as asserted.

Compare the corresponding line in `emitDialectDoc()`:

https://github.com/llvm/llvm-project/blob/0ad6be1927f89cef09aa5d0fb244873f687997c9/mlir/tools/mlir-tblgen/OpDocGen.cpp#L532

Co-authored-by: Malte Dehling <m.dehling@samsung.com>

Author: mdehling

mlir/tools/mlir-tblgen/OpDocGen.cpp

@@ -409,7 +409,7 @@ static void emitEnumDoc(const EnumAttr &def, raw_ostream &os) {
 
 static void emitEnumDoc(const RecordKeeper &records, raw_ostream &os) {
   os << "<!-- Autogenerated by mlir-tblgen; don't manually edit -->\n";
-  for (const Record *def : records.getAllDerivedDefinitions("EnumAttr"))
+  for (const Record *def : records.getAllDerivedDefinitions("EnumAttrInfo"))
     emitEnumDoc(EnumAttr(def), os);
 }