pci: add wrapper for parse_pci

pci: add wrapper for parse_pci

For sbdf's parsing in RMRR command line, add parse_pci_seg with additional
parameter def_seg. parse_pci_seg will help to identify if segment was
found in string being parsed or default segment was used.
Make a wrapper parse_pci so the rest of the callers are not affected.

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Venu Busireddy <venu.busireddy@oracle.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>