drivers: timer: improve sys_timer_disable usage

- Remove the weak symbol definition
- Notify about the capability of disabling via a selected Kconfig option
  (CONFIG_SYSTEM_TIMER_HAS_DISABLE_SUPPORT)
- Provide a dummy inline function when the functionality is not
  available

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
10 files changed