Benjamin Valentin d47a880915 cpu: add periph_rtt_overflow feature
The RTT overflow callback is not available on all RTT implementations.
This means it is either a no-op or `rtt_set_overflow_cb()` is a no-op
or it will overwrite the alarm set with `rtt_set_alarm()`.

This adds a feature to indicate that proper overflow reporting is available.
2021-04-30 11:58:00 +02:00
..
2019-12-12 08:16:54 +01:00
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2020-09-27 18:29:24 -05:00
2021-04-30 11:58:00 +02:00
2020-10-23 00:46:26 +02:00