To allow flexible configuration of IDE introduce HAVE_IDE.
All archs except arm, um and s390 unconditionally select it.
For arm the actual configuration determine if IDE is supported.

This is a step towards introducing drivers/Kconfig for arm.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Russell King - ARM Linux <linux@arm.linux.org.uk>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>