power: supply: sbs-battery: use octal permissions on module param

Symbolic permissions 'S_IRUSR | S_IRGRP | S_IROTH' are not
preferred. Use octal permissions '0444'.

Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>