net: dsa: mv88e6xxx: remove wait and update routines

Now that we have proper Wait Bit and Wait Mask routines, remove the
unused mv88e6xxx_wait routine and its Global 1 and Global 2 variants.

The indirect tables such as the Device Mapping Table or Priority
Override Table make use of an Update bit to distinguish reading (0)
from writing (1) operations. After a write operation occurs, the bit
self clears right away so there's no need to wait on it. Thus keep
things simple and remove the mv88e6xxx_update helper as well.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>