lasips2: change LASIPS2State dev pointer from void to PS2State

lasips2: change LASIPS2State dev pointer from void to PS2State

This allows the compiler to enforce that the PS2 device pointer is always of
type PS2State. Update the name of the pointer from dev to ps2dev to emphasise
this type change.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Helge Deller <deller@gmx.de>
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220712215251.7944-16-mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>