power: supply: bd99954: make read-only array sub_status_reg

Don't populate the read-only array on the stack, instead make it
static const.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>