Make sure sysfs_prefix, when present, is always the first argument
to a function; don't use a different name to refer to it; check
whether it is NULL, and hence SYSFS_SYSTEM_PATH should be used, only
when using it directly and not just passing it down to another
function; always pass down the same value we've been passed when
calling another function.
So far, we are doing compile time decisions on which architecture is
used. However, for testing purposes it's much easier if we pass host
architecture as parameter and then let the function decide which code
snippet for extracting host CPU info will be used.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>