leds: max8997: use mode when calling max8997_led_set_mode

Variable mode is assigned to pdata->led_pdata->mode[led->id] and yet
is not being used when calling function max8997_led_set_mode. Fix
this by using mode when calling max8997_led_set_mode.

Cleans up clang warning:
warning: variable 'mode' set but not used [-Wunused-but-set-variable]

Fixes: 8584cb82 ("leds: Add suuport for MAX8997-LED driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>