conf: Introduce address caching for PCI extensions

conf: Introduce address caching for PCI extensions

This patch provides a caching mechanism for the device address
extensions uid and fid on S390. For efficient sparse address allocation,
we introduce two hash tables for uid/fid which hold the address set
information per domain. Also in order to improve performance of
searching available value, we introduce our own callbacks for the two
hashtables. In this way, uid/fid is saved in hash key and hash value
could be any non-NULL pointer due to no operation on hash value. That is
also the reason why we don't introduce hash value free callback.

Signed-off-by: Yi Min Zhao <zyimin@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>