conf: Introduce parser, formatter for uid and fid

conf: Introduce parser, formatter for uid and fid

This patch introduces new XML parser/formatter functions. Uid is
16-bit and non-zero. Fid is 32-bit. They are the two attributes of zpci
which is introduced as PCI address element. Zpci element is parsed and
formatted along with PCI address. And add the related test cases.

Signed-off-by: Yi Min Zhao <zyimin@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: Stefan Zimmermann <stzi@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>