MLBEDSW-3633: SplitV incorrectly placed on CPU

Minor fix in SPLITV tensor indexing for supported operators check.

Signed-off-by: Jacob Bohlin <jacob.bohlin@arm.com>
Change-Id: If8fa702bfbb25a4a7e5bdb136a19ef72eec7e1c2
diff --git a/ethosu/vela/supported_operators.py b/ethosu/vela/supported_operators.py
index f7dfec2..a1fcf6a 100644
--- a/ethosu/vela/supported_operators.py
+++ b/ethosu/vela/supported_operators.py
@@ -708,7 +708,7 @@
     @staticmethod
     def constraint_splitv_inferred(op):
         "Only one size is allowed to be inferred"
-        sizes = op.ifm2.values
+        sizes = op.inputs[1].values
         valid = np.count_nonzero(sizes == -1) <= 1
         return valid, f"Op has multiple inferred sizes (-1): {sizes}"