ns16550: enable Pericom controller support

ns16550: enable Pericom controller support

Other than the controllers supported so far, multiple port Pericom
boards map all of their ports via BAR0, which requires a number of
adjustments: Instead of tracking "max_bars" we now flag whether all
ports use BAR0, and whether to expect a port-I/O or MMIO resource. As
a result pci_uart_config() now gets handed a port index, which it then
maps into a BAR index or an offset into BAR0 depending on the bar0
flag.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Tim Deegan <tim@xen.org>