spapr: Don't check capabilities removed between CAS calls

We currently check if some capability in OV5 was removed by the guest
since the previous CAS, and we trigger a CAS reboot in that case. This
was required because it could call for a device-tree property or node
removal, that we didn't support until recently (see commit 6787d27b
"spapr: add option vector handling in CAS-generated resets" for details).

Now that we render a full FDT at CAS and that SLOF is able to handle
node removal, we don't need to do a CAS reset in this case anymore.
Also, this check can only return true if the guest has already called
CAS since the last full system reset (otherwise spapr->ov5_cas is
empty). Linux doesn't do that so this can be considered as dead code
for the vast majority of existing setups.

Drop the check. Since the only use of the ov5_cas_old variable is
precisely the check itself, drop the variable as well.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <158514993021.478799.10928618293640651819.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>