spapr: Remove unnecessary 'options' field from sPAPRCapabilityInfo

The options field here is intended to list the available values for the
capability.  It's not used yet, because the existing capabilities are
boolean.

We're going to add capabilities that aren't, but in that case the info on
the possible values can be folded into the .description field.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>