Doesn't work, but at least it makes the dmesg look better.
Index: sys/dev/pci/pcidevs
===================================================================
RCS file: /cvs/src/sys/dev/pci/pcidevs,v
retrieving revision 1.1780
diff -u -p -u -r1.1780 pcidevs
--- sys/dev/pci/pcidevs 28 Nov 2015 14:11:33 -0000 1.1780
+++ sys/dev/pci/pcidevs 6 Dec 2015 20:38:06 -0000
@@ -3102,6 +3102,7 @@ product INTEL BAYTRAIL_LPA 0x0f28 Bay Tr
product INTEL BAYTRAIL_IGD_1 0x0f31 Bay Trail Video
product INTEL BAYTRAIL_IGD_2 0x0f32 Bay Trail Video
product INTEL BAYTRAIL_IGD_3 0x0f33 Bay Trail Video
+product INTEL BAYTRAIL_EHCI 0x0f34 Bay Trail EHCI
product INTEL BAYTRAIL_XHCI 0x0f35 Bay Trail xHCI
product INTEL BAYTRAIL_8237 0x0f40 Bay Trail I2C DMA
product INTEL BAYTRAIL_I2C_1 0x0f41 Bay Trail I2C
