When all 64-bits of the signal value are 0, we can skip polling for that
signal.
We need to keep signals as 64-bit numbers as part of the spec. But most
users of ROCr do will never set the signal value to more than 32-bits.
When the dependent-signals are less than 32-bits, avoid adding extra
SDMA poll packet as this adds latency to the SDMA copies.
Change-Id: I37dca65fe3f060dc7164f49b98cb1985023663c4
David Yat Sin
0544c2336b