XTIMER_BACKOFF and XTIMER_ISR_BACKOFF were defined in periph_conf.h
since 2016 for the legacy xtimer module, which required high backoff
values (200) on native to prevent timer underflow issues.
However, since the migration to ztimer, all code now uses
MODULE_ZTIMER_XTIMER_COMPAT which includes ztimer/xtimer_compat.h
before periph_conf.h. This means xtimer_compat.h always defines
XTIMER_BACKOFF=1 first, and the periph_conf.h definitions are never
used.
Remove these unused definitions as they serve no purpose with the
current ztimer-based implementation.
Signed-off-by: Gilles DOFFE <g.doffe@gmail.com>
aab432ff6d