Update functons used to count number of FC hosts

Update functons used to count number of FC hosts

Update/improve functions used to count number of FC hosts:
1) Move code used to count hosts from sa_wrap.c to its normal location
(count.c).
2) Preallocate FC host structures to take into account a possibly
dynamically registerd host. No structures are allocated only if
/sys/class/fc_host directory is not found.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>