arch/xtensa/core: Fix timing API issues

Two issues:
 - A unnecessary parentheses pair caused rounding errors (by truncating
   a small value before multiplying it).
 - arch_timing_cycles_to_ns_avg() wasn't actually converting the result
   to nanoseconds.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>
1 file changed