ide: ide.c 'clear' fix, update "ide=nodma" documentation

ide: ide.c 'clear' fix, update "ide=nodma" documentation

Documentation/kernel-parameters.txt
- ide=nodma is no longer valid.

drivers/ide/Kconfig
- The module is ide-core.ko not ide.

drivers/ide/ide.c
- It took me a while to figure out what the arguments %d.%d:%d to nodma
  module parameter ment, so I added a comment to each.
- Added a comment to each of the sscanf lines.
- There is a bug, if j is 0 it would previously clear all the other bits
  except the current device, changed in three different places.
  mask &= (1 << i) should be mask &= ~(1 << i).

Signed-off-by: David Fries <david@fries.net>
[bart: s/disk/device/ in ide.c, beautify patch description]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>