corrected the description example !llvm.ptr to memref<*xbf16>

Author: arun-thmn

mlir/include/mlir/Dialect/X86Vector/X86Vector.td

@@ -425,7 +425,7 @@ def CvtPackedEvenIndexedBF16ToF32Op : AVX_Op<"cvt.packed.even.indexed.bf16_to_f3
 
     Example:
     ```mlir
-    %dst = x86vector.avx.cvt.packed.even.indexed.bf16_to_f32 %a : !llvm.ptr -> vector<8xf32>
+    %dst = x86vector.avx.cvt.packed.even.indexed.bf16_to_f32 %a : memref<16xbf16> -> vector<8xf32>
     ```
   }];
   let arguments = (ins AnyMemRef:$a);
@@ -461,7 +461,7 @@ def CvtPackedOddIndexedBF16ToF32Op : AVX_Op<"cvt.packed.odd.indexed.bf16_to_f32"
 
     Example:
     ```mlir
-    %dst = x86vector.avx.cvt.packed.odd.indexed.bf16_to_f32 %a : !llvm.ptr -> vector<8xf32>
+    %dst = x86vector.avx.cvt.packed.odd.indexed.bf16_to_f32 %a : memref<16xbf16> -> vector<8xf32>
     ```
   }];
   let arguments = (ins AnyMemRef:$a);
@@ -502,7 +502,7 @@ def BcstBF16ToPackedF32Op : AVX_Op<"bcst.bf16_to_f32.packed", [MemoryEffects<[Me
 
     Example:
     ```mlir
-    %dst = x86vector.avx.bcst.bf16_to_f32.packed %a : !llvm.ptr -> vector<8xf32>
+    %dst = x86vector.avx.bcst.bf16_to_f32.packed %a : memref<1xbf16> -> vector<8xf32>
     ```
   }];
   let arguments = (ins AnyMemRef:$a);