INT 1A - PCI BIOS v2.0c+ - READ CONFIGURATION BYTE (32-bit)

	AX = B188h
	BH = bus number
	BL = device/function number (bits 7-3 device, bits 2-0 function)
	DI = register number (0000h-00FFh)
Return: as for AX=B108h
Note:	the meanings of BL and BH on return were exchanged between the initial
	  drafts of the specification and final implementation
SeeAlso: AX=B108h,AX=B189h,AX=B18Ah