utils: Fix implicit declaration
The declaration was still using the old name.
src/ppd-action-trickle-charge.c: In function ‘set_charge_type’:
src/ppd-action-trickle-charge.c:61:5: warning: implicit declaration of function ‘ppd_utils_write_sysfs’ [-Wimplicit-function-declaration]
61 | ppd_utils_write_sysfs (dev, CHARGE_TYPE_SYSFS_NAME, charge_type, NULL);
| ^~~~~~~~~~~~~~~~~~~~~