Qais Yousef authored Oct 11, 2019 and Ionela Voinescu committed Aug 02, 2021

SPAN_SIZE was being set to 0 when NR_CPUS was 2; which triggererd
a compile time assertion. Which exposed a bug in the logic where we
where rounding down instead of up. Fix it by using round_up() to ensure
we get the correct span size for the NR_CPUS.

Ensure as well that we don't use a spansize greather than 128. The trace
str can't take arbitrarly large size. It's limited to 256 but be more
conservative and cap it to 128.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>