realtek: consistently flood RMA frames

realtek: consistently flood RMA frames

The switches support different actions for incoming ethernet multicast
frames with Reserved Multicast Addresses (01-80-C2-00-00-{01-2F}). The
current code will set the 2-bit action field to FLOOD (0x3) for most
classes, but the highest bit is always unset for the relevant control
registers. This means the DROP (0x1) action being used for these
classes; whatever class the MSB happens to be in.

For RTL838x, this results in {20,23-2F} frames being dropped, instead of
flooding all ports. On other switch generations, {0F,1F,2F} frames are
dropped. This is inconsistent, and appears to be a mistake. Remove this
inconsistency by flooding all multicast frames with RMA addresses.

Signed-off-by: Sander Vanheule <sander@svanheule.net>