pckbd: don't use legacy ps2_mouse_init() function

pckbd: don't use legacy ps2_mouse_init() function

Instantiate the PS2 mouse device within KBDState using
object_initialize_child() in i8042_initfn() and i8042_mmio_init() and realize
it in i8042_realizefn() and i8042_mmio_realize() accordingly.

Signed-off-by: Mark Cave-Ayland <[email protected]>
Tested-by: Helge Deller <[email protected]>
Acked-by: Helge Deller <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Message-Id: <20220712215251[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>