devicetree: bindings: Properly document micrel ks8851 SPI chips

devicetree: bindings: Properly document micrel ks8851 SPI chips

The ks8851 SPI ethernet wasn't documented, but we documented the
optional regulator supply for it under the mll based ethernet
chip. Furthermore, that compatible string needed another 'l'. Fix
all of this and document the optional vdd-io and reset-gpios
properties.

Cc: Nishanth Menon <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Pawel Moll <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Ian Campbell <[email protected]>
Cc: Kumar Gala <[email protected]>
Cc: <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
Signed-off-by: David S. Miller <[email protected]>