ARM: dts: imx: Use flash@0,0 pattern

ARM: dts: imx: Use flash@0,0 pattern

Per mtd-physmap.yaml, 'nor@0,0' is not a valid node pattern.

Change it to 'flash@0,0' to fix the following dt-schema warning:

imx1-ads.dtb: nor@0,0: $nodename:0: 'nor@0,0' does not match '^(flash|.*sram|nand)(@.*)?$'
	from schema $id: http://devicetree.org/schemas/mtd/mtd-physmap.yaml#

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>