m68k/atari: Convert Falcon IDE drivers to platform drivers

Autoloading of Falcon IDE driver modules requires converting these
drivers to platform drivers.

Add platform device for Falcon IDE interface in Atari platform setup
code. Use this in the pata_falcon driver in place of the simple
platform device set up on the fly.

Convert falconide driver to use the same platform device that is used
by pata_falcon also. (With the introduction of a platform device for
the Atari Falcon IDE interface, the old Falcon IDE driver no longer
loads (resource already claimed by the platform device)).

Tested (as built-in driver) on my Atari Falcon.

Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://lore.kernel.org/r/1573008449-8226-1-git-send-email-schmitzmic@gmail.com
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>