puc: Add support for Systembase SB16C1054, SB16C1058.

The Systembase SB16C1054 and SB16C1058 are PCI quad- and octal-UART
complexes, based on multiple Systembase SB16C1050 cores, which appear to
be compatible with the NS8250 family (except for the "enable interrupts"
bit in the other BAR).

The SB16C105x family are one of two families of PCIe UART complexes on
cards by StarTech.com, such as the PEX4S1050 and PEX8S1050. (Other
StarTech.com serial offerings use the ASIX AX99100 or ASIX MCS990x.)

This is derived from the NetBSD driver.

Reviewed by: imp
Tested by: Jashank Jeremy <jashank@rulingia.com.au>
Obtained from: Jashank Jeremy <jashank@rulingia.com.au>
MFC after: 1 week
Differential Revision: <https://reviews.freebsd.org/D52150