INT 15 - EISA SYSTEM ROM - CLEAR NONVOLATILE MEMORY (EISA CMOS)
        AX = D802h
        BH = EISA config utility major revision level
        BL = EISA config utility minor revision level
Return: CF clear if successful
            AH = 00h
        CF set on error
            AH = error code
                84h error clearing CMOS
                86h invalid BIOS-FW function call
                88h config utility version not supported
Note:   call with AL=82h if using 32-bit CS addressing mode instead of 16-bit