ks8851: Update link status during link change interrupt

If a link change interrupt comes in we just clear the interrupt
and continue along without notifying the upper networking layers
that the link has changed. Use the mii_check_link() function to
update the link status whenever a link change interrupt occurs.

Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>