hw/sd/sdcard: Update the SDState documentation

Add more descriptive comments to keep a clear separation
between static property vs runtime changeable.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20200630133912.9428-12-f4bug@amsat.org>
1 file changed