RMII receive does not handle extra nibble at the end of the frame

[shuchitak]

test_4_1_9.py tests by sending frames that have an extra nibble padded after the CRC word. The MII receiver due to receiving at a nibble boundary (32bit buffered 4bit data port) is able to receive and discard this extra nibble.

 /* Correct for non byte-aligned frames */
  tail <<= taillen & 0x7;

This wouldn't work for the RMII receiver.

I'm not sure if having the capability to correctly receive frames that have only 1 extra nibble (while dropping frames with more than 1 extra nibbles after the CRC word) at the end of the frame is required.