Refactor mii monitor.  As with the previous ARP monitor refactor,
the motivation for this is to handle locking rationally (in this case,
removing conditional locking) and generally clean up the code.

	This patch breaks up the monolithic mii monitor into two phases:
an inspection phase, followed by an optional commit phase.  The commit phase
is the only portion that requires RTNL or makes changes to state, and is
only called when inspection finds something to change.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>