net: pcs: xpcs: don't use array for interface

net: pcs: xpcs: don't use array for interface

Currently, xpcs uses an array of interfaces that each "compat" entry
supports. When looking up the compat entry for an interface, we
iterate over the compat entries and then over each interface.

Since each compat entry only has a single interface in its interfaces
array, replace the array with a single member in the compat structure.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>