hw/sd/pl181: Use named GPIOs

hw/sd/pl181: Use named GPIOs

To make the code easier to manage/review/use, rename the
cardstatus[0] variable as 'card_readonly' and name the GPIO
"card-read-only".
Similarly with cardstatus[1], renamed as 'card_inserted' and
name its GPIO "card-inserted".

Adapt the users accordingly by using the qdev_init_gpio_out_named()
function.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200705204630.4133-6-f4bug@amsat.org>