This shrinks the size of the structure on arm64 by 8 bytes by avoiding
padding of 4 bytes at two places.

Also add missing doc comment for freq_table
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: NLukasz Luba <lukasz.luba@arm.com>
Tested-by: NLukasz Luba <lukasz.luba@arm.com>
Signed-off-by: NEduardo Valentin <edubezval@gmail.com>