ARM: dts: imx6sx: Fix spba-bus unit address

The correct unit address for spba-bus is 0x2240000, so change it
accordingly in order to fix the following build warning with W=1:

arch/arm/boot/dts/imx6sx-sabreauto.dtb: Warning (simple_bus_reg): Node /soc/aips-bus@2200000/spba-bus@2200000 simple-bus unit address format error, expected "2240000"

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>