Arm backend: Reject INT16-matmuls on U55 (pytorch#18365)

Make sure that INT16 matmuls are rejected for U55.


cc @digantdesai @freddan80 @per @zingo @mansnils @Sebastian-Larsson
@robell

Signed-off-by: Oscar Andersson <oscar.andersson@arm.com>

Author: oscarandersson8218

backends/arm/operator_support/ethos_u55_support.py

@@ -157,10 +157,10 @@ def is_node_supported(  # noqa: C901
         ):
             for input_node in node.all_input_nodes:
                 dtype = _try_determine_dtype(input_node)
-                if dtype is not None and dtype not in (torch.int8, torch.int16):
+                if dtype is not None and dtype not in (torch.int8,):
                     self.reporter.report_reject(
-                        input_node,
-                        f"Input {input_node.name} has unsupported dtype {dtype} (Supports i8, i16).",
+                        node,
+                        f"Input {input_node.name} has unsupported dtype {dtype} (Supports int8).",
                     )
                     return False