FastCAM for EfficientNet

[niladridutt]

Is your feature request related to a problem? Please describe. EfficientNet is widely used owing to its speed and accuracy. Since EfficientNet uses Swish unlike ResNet which uses ReLU it would be very helpful to have a version of FastCAM tailored for EfficientNet

Describe the solution you'd like FastCAM implementation on EfficientNet which takes into account Swish activation fn