The ADVANCED_TIMERS define/check was added in 523943a as part of adding L1
support. The runtime checks against TIM1/TIM8 already existed. Since L1
doesn't have TIM1/TIM8, those names are undefined, resulting in a compilation
error until ifdeffed out.
Since I throw out all TIM1/TIM8 checks, there's no references to those names
left, thus no need to keep the ifdef either.
As for the registers themselves, l1/timer.h pulls in common/timer_common_all.h
which defines macros for the superset of all timers, so e.g. TIM_BDTR() is
still available regardless of whether or not the particular chip we're building
for has any timers with a BDTR register.
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