net: ks8851: Add of match table

Users are currently just providing "ks8851" as the compatible for
this driver in device tree. Add a compatible string that provides
the vendor name along with the device name to be more explicit.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>