ide: cable detection fixes (take 2)

Tejun's recent eighty_ninty_three() fix has inspired me to do more thorough
review of the cable detection code...

* print user-friendly warning about limiting the maximum transfer speed
  to UDMA33 (and the reason behind it) when 80-wire cable is not detected,
  also while at it cleanup eighty_ninty_three() a bit

* use eighty_ninty_three() in ide_ata66_check(), this actually fixes 3 bugs:
  - bit 14 (word 93 validity check) == 1 && bit 13 (80-wire cable test) == 1
    were used as 80-wire cable present test for CONFIG_IDEDMA_IVB=n case
    (please see FIXME comment in eighty_ninty_three() for more details)
  - CONFIG_IDEDMA_IVB=y/n cases were interchanged
  - check for SATA devices was missing

* remove private cable warnings from pdc_202xx{old,new} drivers now that core
  code provides this functionality (plus, in pdc202xx_new case the test could
  give false warnings for ATAPI devices because pdc202xx_new driver doesn't
  even support ATAPI DMA)

Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

diff --git a/include/linux/ide.h b/include/linux/ide.h
index 477b8c6..ca924b2 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -605,6 +605,7 @@
 	unsigned scsi		: 1;	/* 0=default, 1=ide-scsi emulation */
 	unsigned sleeping	: 1;	/* 1=sleeping & sleep field valid */
 	unsigned post_reset	: 1;
+	unsigned udma33_warned	: 1;
 
 	u8	addressing;	/* 0=28-bit, 1=48-bit, 2=48-bit doing 28-bit */
         u8	quirk_list;	/* considered quirky, set for a specific host */