Fix nxp unittests

[larryliu0820]

Let's not hard code the number of nodes in the graph.

The graph of batch norm + conv looks like this after torch nightly 1015:

graph():
    %p_conv_weight : [num_users=1] = placeholder[target=p_conv_weight]
    %p_conv_bias : [num_users=1] = placeholder[target=p_conv_bias]
    %p_batch_norm_batch_norm_weight : [num_users=1] = placeholder[target=p_batch_norm_batch_norm_weight]
    %p_batch_norm_batch_norm_bias : [num_users=1] = placeholder[target=p_batch_norm_batch_norm_bias]
    %b_batch_norm_batch_norm_running_mean : [num_users=1] = placeholder[target=b_batch_norm_batch_norm_running_mean]
    %b_batch_norm_batch_norm_running_var : [num_users=1] = placeholder[target=b_batch_norm_batch_norm_running_var]
    %x : [num_users=1] = placeholder[target=x]
    %conv2d : [num_users=1] = call_function[target=torch.ops.aten.conv2d.default](args = (%x, %p_conv_weight, %p_conv_bias), kwargs = {})
    %batch_norm : [num_users=1] = call_function[target=torch.ops.aten.batch_norm.default](args = (%conv2d, %p_batch_norm_batch_norm_weight, %p_batch_norm_batch_norm_bias, %b_batch_norm_batch_norm_running_mean, %b_batch_norm_batch_norm_running_var, False, 0.1, 1e-05, True), kwargs = {})
    return (batch_norm,)

[pytorch-bot]

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✅ You can merge normally! (2 Unrelated Failures)

As of commit 5455390 with merge base cf407fc ():

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / linux / linux-job (gh) (trunk failure)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)

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