Many different architectures re-implemented the exact same code for
`up_*delay` because it was originally written as architecture dependent
code. Busy-waiting can be done regardless of architecture, so this
commit moves that duplicated implementation to a common file with weak
definitions so that individual architectures (see tc32) are still able
to override the definition if needed/desired.
Default implementation is not included if ARCH_TIMER is enabled, since
it is more accurate and provides its own weak definitions to override.
Signed-off-by: Matteo Golin <matteo.golin@gmail.com>
