Separate USB_RX_EARLY_AGG into USB_RX_EARLY_TIMEOUT and USB_RX_EARLY_SIZE.

Replace r8153_set_rx_agg() with r8153_set_rx_early_timeout() and
r8153_set_rx_early_size().

Set the default timeout value according to the USB speed.
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>