net: emaclite: Remove unnecessary code that enables/disables interrupts on PONG buffers

There are no specific interrupts for the PONG buffer on both
transmit and receive side, same interrupt is valid for both
buffers. So, this patch removes this code.

Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
Reviewed-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>