Add padPlace: LazyScope value

background: At the request of the physical implementation & design team,
 	    we needed a space to put the pad in one place.
	    So I created a value called padPlace.
            padPlace default value is shell.

Add def padPlace: LazyScope = shell in IOPlacedOverlay trait

Changed the existing sink scope from shell to padPlace.
  in GPIOPlacedOverlay, I2CPlacedOverlay, JTAGDebugPlacedOverlay,
     PWMPlacedOverlay, SPIFlashPlacedOverlay, UARTPlacedOverlay