With a new configuration option one can now remove the need for
repeatedly calling `lv_tick_inc` for hardware that already provides
system time in another way.
The configuration example is set for an Arduino, but this was initially
developed for an nrf52 with the following config:
```
#define LV_TICK_CUSTOM 1
#if LV_TICK_CUSTOM == 1
#define LV_TICK_CUSTOM_INCLUDE "app_timer.h"
#define LV_TICK_CUSTOM_SYS_TIME_EXPR (app_timer_cnt_get()/APP_TIMER_TICKS(1))
#endif /*LV_TICK_CUSTOM*/
```
