INT 21 - MS-DOS 7.0+ - GENERIC IOCTL - UNLOCK PHYSICAL VOLUME

	AX = 440Dh
	CX = 086Bh / 486Bh
	    (category code 08h for FAT12/16, 48h for FAT32; minor code 6Bh)
	BH = logical drive number (00h = default, 01h = A:, etc.)
Return: CF set on error
	    AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
Desc:	lock all logical volumes on the same physical volume as the indicated
	  drive
SeeAlso: AX=440Dh"DOS 3.2+",AX=440Dh/CX=084Bh,AX=440Dh/CX=086Ah