mcb: use short version for function pointer for mcb_free_bus

Just a style change so that the device release callbacks are defined
in the same way for devices in mcb_bus and mcb_device.

Signed-off-by: Jorge Sanjuan Garcia <jorge.sanjuangarcia@duagon.com>
Co-developed-by: Jose Javier Rodriguez Barbarin <JoseJavier.Rodriguez@duagon.com>
Signed-off-by: Jose Javier Rodriguez Barbarin <JoseJavier.Rodriguez@duagon.com>
Link: https://lore.kernel.org/r/20230906114901.63174-3-JoseJavier.Rodriguez@duagon.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>