INT 1A - Intel PCI BIOS v2.0c - FIND PCI CLASS CODE
        AX = B103h
        ECX = class code (bits 23-0)
        SI = device index (0-n)
Return: CF clear if successful
        CF set on error
        AH = status
            00h successful
                BL = bus number
                BH = device/function number (bits 7-3 device, bits 2-0 func)
            86h device not found
        EAX, EBX, ECX, and EDX may be modified
        all other flags (except IF) may be modified
Notes:  this function may require up to 1024 byte of stack; it will not enable
          interrupts if they were disabled before making the call
        the meanings of BL and BH on return may be exchanged in future
          implementations
        all devices sharing the same Class Code may be enumerated by
          incrementing SI from 0 until error 86h is returned
SeeAlso: AX=B183h

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