feat: add torch._VF.lstm frontend

ivy/functional/backends/tensorflow/layers.py

@@ -790,7 +790,7 @@ def lstm_update(
     recurrent_bias = (
         recurrent_bias.data if recurrent_bias is not None else recurrent_bias
     )
-    if "cpu" in dev:
+    if "cpu" in dev.lower():
         outputs, new_states = _cpu_lstm(
             x,
             init_h,

ivy/functional/frontends/torch/_VF/__init__.py

@@ -0,0 +1,4 @@
+import ivy.functional.frontends.torch as torch_frontend
+
+def lstm(*args, **kwargs):
+    return torch_frontend.lstm(*args, **kwargs)

ivy/functional/frontends/torch/__init__.py

@@ -268,6 +268,7 @@ def promote_types_of_torch_inputs(
 from .nn.functional import softmax, relu, lstm
 from . import special
 from . import tensor
+from . import _VF
 from .tensor import *
 from . import blas_and_lapack_ops
 from .blas_and_lapack_ops import *