re: kern/57015: sdhc fails for Ricoh 5U823 controller

[matthew green <mrg%eterna.com.au@localhost>]

this hack also fixes the previously working but broken sometime
in the last couple of years sdhc in my kabylake laptop, though
it's a different chipset:

rtsx0 at pci8 dev 0 function 0: Realtek Semiconductor RTS525A PCI-E Card Reader (rev. 0x01)
rtsx0: interrupting at msi4 vec 0
sdmmc0 at rtsx0
[ .. ]
ld1 at sdmmc0: <0x03:0x5344:SN256:0x80:0x8a389e07:0x138>
ld1: 238 GB, 31107 cyl, 255 head, 63 sec, 512 bytes/sect x 499744768 sectors
ld1: 4-bit width, 25.000 MHz


.mrg.