mtd: onenand: make onenand/generic.c more generic

Remove the ARM dependency from the generic "onenand" platform device
driver.  This change makes the driver useful for other architectures as
well.  Needed for the SuperH kfr2r09 board.

Apart from the obvious Kconfig bits, the most important change is the move
away from ARM specific includes and platform data.  Together with this
change the only in-tree board code gets an update, and the driver name is
also changed gracefully break potential out of tree drivers.

The driver is also updated to allow NULL as platform data together with a
few changes to make use of resource_size() and dev_name().

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Kyungmin Park <kmpark@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>