Replace open-coded time conversion with the macro which as that will
usually use a constant divide or multiply.
Signed-off-by: Keith Packard <keithp@keithp.com>
This allows for builds with CONFIG_SYS_CLOCK_EXISTS=n in which case
busy waits are achieved with a crude CPU loop. If ever accuracy is
needed even with such a configuration then implementing arch_busy_wait()
should be considered.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>