via-rhine: Add platform dependencies

The VIA Rhine Ethernet interface is only present on PCI devices or
VIA/WonderMedia VT8500/WM85xx SoCs.  Add platform dependencies to the
VIA_RHINE config symbol, to avoid asking the user about it when
configuring a kernel without PCI or VT8500/WM85xx support.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>