Disable MSI on Zhaoxin ZX-100/ZX-200/ZX-E StorX to unhang SSD

Disable MSI on Zhaoxin ZX-100/ZX-200/ZX-E StorX to unhang SSD

The Unchartevice 6640MA's BIOS forces one of three SATA speeds:
- Gen1/2: bsd.rd reaches installer, but SSD does not attach
- Gen3:   bsd.rd attaches SSD but hangs

MSI works for iwm(4) and and xhci(4), only ahci(4) bugs out, so add a quirk
for this controller as done for a few other devices already:

 ahci0 at pci0 dev 15 function 0 "Zhaoxin StorX AHCI" rev 0x01: apic 9 int 21, AHCI 1.3.1
-ahci0: device not communicating on port 0
+ahci0: port 0: 6.0Gb/s
 scsibus0 at ahci0: 32 targets
+sd0 at scsibus0 targ 0 lun 0: <ATA, 256GB SSD, V1.3> naa.5000000000000000
+sd0: 244198MB, 512 bytes/sector, 500118192 sectors, thin

OK kettenis