net: encx24j600: Fix mask to update LED configuration

This fixes the mask used to update the LED configuration so that it clears
the necessary bits as well as setting the bits according to the mask.
Also reverse the LED configuration to show the Link state + collisions in
LEDA and the Link state + TX/RX events in LEDB.

Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: David S. Miller <davem@davemloft.net>