staging: mmal-vchiq: If the VPU returns an error, don't negate it

There is an enum for the errors that the VPU can return.
port_parameter_get was negating that value, but also using -EINVAL
from the Linux error codes.
Pass the VPU error code as positive values. Should the function
need to pass a Linux failure, then return that as negative.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-7-nsaenzjulienne@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c

@@ -1270,7 +1270,8 @@ static int port_parameter_get(struct vchiq_mmal_instance *instance,
 		goto release_msg;
 	}
 
-	ret = -rmsg->u.port_parameter_get_reply.status;
+	ret = rmsg->u.port_parameter_get_reply.status;
+
 	/* port_parameter_get_reply.size includes the header,
 	 * whilst *value_size doesn't.
 	 */