KVM: arm64: vgic: Do not ignore vgic_its_restore_cte failures

Restoring a corrupted collection entry (like an out of range ID) is
being ignored and treated as success. More specifically, a
vgic_its_restore_cte failure is treated as success by
vgic_its_restore_collection_table.  vgic_its_restore_cte uses positive
and negative numbers to return error, and +1 to return success.  The
caller then uses "ret > 0" to check for success.

Fix this by having vgic_its_restore_cte only return negative numbers on
error.  Do this by changing alloc_collection return codes to only return
negative numbers on error.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220510001633.552496-4-ricarkol@google.com