net: phy: sfp: rename dt properties to match the binding

Make the Rx rate select control gpio property name match the documented
binding. This would make the addition of 'rate-select1-gpios' for SFP+
support more natural.

Also, make the MOD-DEF0 gpio property name match the documentation.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>