ide: remove unused ide_hwif_t.sg_mapped field

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

include/linux/ide.h

@@ -817,7 +817,6 @@ typedef struct hwif_s {
 	unsigned	extra_ports;	/* number of extra dma ports */
 
 	unsigned	present    : 1;	/* this interface exists */
-	unsigned	sg_mapped  : 1;	/* sg_table and sg_nents are ready */
 	unsigned	busy	   : 1; /* serializes devices on a port */
 
 	struct device		gendev;