[Quantization] Fix annotation for multiply op

[masahi]

When I tried to quantize a model with squeeze and excitation block, I hit the error at this line. The RHS of the multiply op should be checked for being constant, rather than hardcoded as weight.

[masahi]

@vinx13 I'm trying to get a simple quantization test case working. How can I get an int8 output from below? I'm getting FP32 result.

UPDATE: I need to add skip_conv_layers=[] to qconfig to force quantization on the first conv layer. But then I get an error at MulRealize. Working on it.

    data = relay.var("data", shape=(1, 16, 64, 64))
    conv = relay.nn.conv2d(data, relay.var("weight"),
                           kernel_size=(3, 3),
                           padding=(1, 1),
                           channels=16)
    act = relay.nn.relu(data=conv)
    pool = relay.nn.global_avg_pool2d(data=act)
    f = relay.Function(relay.analysis.free_vars(act), act * pool)
    mod, params = testing.create_workload(f)

    with relay.quantize.qconfig():
        print(relay.quantize.quantize(mod, params))

[masahi]

Is there a deep reason for having this check?

[vinx13]

this check seems very trivial... @ZihengJiang ?

[masahi]

@vinx13 @ZihengJiang ready for review.

[masahi]

ping @vinx13 @ZihengJiang can we merge this?