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.

Change-Id: I71f7405418dd4af003dfc263733133bbe529c212
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>