[Relay] Expose qnn ops directly from relay.qnn module

When we access `nn` ops in relay, we can directly access them as
`relay.nn.<op>` where `<op>` can be any nn op like `conv2d`,
`avg_pool2d`, etc.

When we access `qnn` ops, we need to access them as `relay.qnn.op.<op>`
as they're not exposed to the `relay.qnn` module. This change tries to
add that.

python/tvm/relay/qnn/__init__.py

@@ -14,8 +14,9 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-# pylint: disable=wildcard-import
+# pylint: disable=wildcard-import,redefined-builtin
 """QNN dialect operators and IR passes."""
 from __future__ import absolute_import as _abs
 from . import op
 from . import transform
+from .op.qnn import *