ide: add IDE_HFLAG_CLEAR_SIMPLEX host flag

* Rename 'simplex_stat' variable to 'dma_stat' in ide_get_or_set_dma_base().

* Factor out code for forcing host out of "simplex" mode from
  ide_get_or_set_dma_base() to ide_pci_clear_simplex() helper.

* Add IDE_HFLAG_CLEAR_SIMPLEX host flag and set it in alim15x3 (for M5229),
  amd74xx (for AMD 7409), cmd64x (for CMD643), generic (for Netcell) and
  serverworks (for CSB5) host drivers.

* Make ide_get_or_set_dma_base() test for IDE_HFLAG_CLEAR_SIMPLEX host flag
  instead of checking dev->device (BTW the code was buggy because it didn't
  check for dev->vendor, luckily none of these PCI Device IDs was used by
  some other vendor for PCI IDE controller).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/cmd64x.c b/drivers/ide/pci/cmd64x.c
index cd4eb9d..effd79a 100644
--- a/drivers/ide/pci/cmd64x.c
+++ b/drivers/ide/pci/cmd64x.c
@@ -443,7 +443,9 @@
 		.init_chipset	= init_chipset_cmd64x,
 		.init_hwif	= init_hwif_cmd64x,
 		.enablebits	= {{0x00,0x00,0x00}, {0x51,0x08,0x08}},
-		.host_flags	= IDE_HFLAG_ABUSE_PREFETCH | IDE_HFLAG_BOOTABLE,
+		.host_flags	= IDE_HFLAG_CLEAR_SIMPLEX |
+				  IDE_HFLAG_ABUSE_PREFETCH |
+				  IDE_HFLAG_BOOTABLE,
 		.pio_mask	= ATA_PIO5,
 		.mwdma_mask	= ATA_MWDMA2,
 		.udma_mask	= 0x00, /* no udma */