mtd: orion_nand: remove <mach/hardware.h> include

Commit abcda1dc ('arm: plat-orion: introduce PLAT_ORION_LEGACY hidden
config option') currently pending in linux-next will make the ARCH_MVEBU
platform select PLAT_ORION, which means that now all Orion drivers can
be enabled on ARCH_MVEBU. This works fine for most drivers, except for
orion_nand, because it includes <mach/hardware.h>, but mach-mvebu does
not have a mach/hardware.h header (it is considered as a deprecated
practice).

It turns out that the <mach/hardware.h> include in orion_nand is not
necessary: the driver builds perfectly fine without it, so we simply
get rid of it.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>