Refactored sysinfo public functions, simplified usage

Signed-off-by: Haru <haru@dotalux.com>
Whitespace cleanup

Replaced some tabs in the middle of the line with spaces.
Thanks to KeiKun for pointing out #ifdef<tab>_COMMON_SYSINFO_H_ and
making me realize how many of them were there.

Signed-off-by: Haru <haru@dotalux.com>