block: Clarify documentation of BlockInfo member io-status

Say "SCSI except scsi-generic" instead of "scsi-disk", because
scsi-disk could mean either scsi-disk.c (which is correct) or device
model scsi-disk (which would be incorrect).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1494327362-30727-2-git-send-email-armbru@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>

qapi/block-core.json

@@ -449,7 +449,8 @@
 #
 # @io-status: @BlockDeviceIoStatus. Only present if the device
 #             supports it and the VM is configured to stop on errors
-#             (supported device models: virtio-blk, ide, scsi-disk)
+#             (supported device models: virtio-blk, IDE, SCSI except
+#             scsi-generic)
 #
 # @inserted: @BlockDeviceInfo describing the device if media is
 #            present