power: supply: rk817: check correct variable

This code checks "->chg_ps" twice when it was supposed to check
"->bat_ps".

Fixes: 11cb8da0 ("power: supply: Add charger driver for Rockchip RK817")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>