net: dsa: mv88e6xxx: add mv88e6250_g1_ieee_pri_map

Quite a few of the existing supported chips that use
mv88e6085_g1_ieee_pri_map as ->ieee_pri_map (including, incidentally,
mv88e6085 itself) actually have a reset value of 0xfa50 in the
G1_IEEE_PRI register.

The data sheet for the mv88e6095, however, does describe a reset value
of 0xfa41.

So rather than changing the value in the existing callback, introduce
a new variant with the 0xfa50 value. That will be used by the upcoming
mv88e6250, and existing chips can be switched over one by one,
preferably double-checking both the data sheet and actual hardware in
each case - if anybody actually feels this is important enough to
care.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>