net/dp8393x: remove check of runt packets

Ethernet requires that messages are at least 64 bytes on the wire. This
limitation does not exist on emulation (no wire message), so remove the
check. Netcard is now able to receive small network packets.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
