A new binding for flash devices was recently introduced.  This updates the
Sequoia DTS to use the new binding and enabled MTD in the defconfig.
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: NDavid Gibson <david@gibson.dropbear.id.au>
Acked-by: NStefan Roese <sr@denx.de>