power: supply: core: Use true and false for bool variable

Fix the following coccicheck warning:

./include/linux/power_supply.h:507:9-10: WARNING: return of 0/1 in
function 'power_supply_is_watt_property' with return type bool.

./include/linux/power_supply.h:479:9-10: WARNING: return of 0/1 in
function 'power_supply_is_amp_property' with return type bool.

Reported-by: Abaci <Robot&lt;abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>