ide: remove stale comments from ide-dma.c (take 2)

- ide-dma.c is not a separate module

- ide-dma.c is not PCI specific anymore

- DMA is enabled by default nowadays

- link for Intel Zappa BIOS is dead

etc.

v2:
* Some comments should be preserved. (Noticed by Mark Lord)

Cc: Mark Lord <liml@rtr.ca>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>