ide: always set nIEN on idle devices

* Set nIEN for previous port/device in ide_do_request()
  also if port uses a non-shared IRQ.

* Remove no longer needed ide_hwif_t.sharing_irq.

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

include/linux/ide.h

@@ -842,7 +842,6 @@ typedef struct hwif_s {
 
 	unsigned	present    : 1;	/* this interface exists */
 	unsigned	serialized : 1;	/* serialized all channel operation */
-	unsigned	sharing_irq: 1;	/* 1 = sharing irq with another hwif */
 	unsigned	sg_mapped  : 1;	/* sg_table and sg_nents are ready */
 
 	struct device		gendev;