net: ks8851: Fix register macro misnomers

In the header file accompanying the ks8851 driver, the P1SCLMD register
macros are misnamed, they actually pertain to the P1CR register.

The P1CR macros in turn pertain to the P1SR register, see pages 65 to 68
of the spec:
http://www.hqchip.com/uploads/pdf/201703/47c98946d6c97a4766e14db3f24955f2.pdf



The misnomers have no negative consequences so far because the macros
aren't used by ks8851.c, but that's about to change.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Tristram Ha <Tristram.Ha@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>