arch: m68k: q40: README: drop references to IDE driver

Since IDE support was deleted by Christoph Hellwig <hch@lst.de>,
Jun 16 2021, drop the left-over from README file, updating the
documentation to point to ata/pata_falcon.c.

Fixes: 44b1fbc0 ("m68k/q40: Replace q40ide driver with pata_falcon and falconide")
Fixes: b7fb14d3 ("ide: remove the legacy ide driver")
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/d6e3482ed622b6953db69cddb70f20c55c96e4da.1656234456.git.mchehab@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>