ARM: dts: imx7d-sdb: Put pinctrl_spi4 in the correct location

pinctrl_spi4 pin group is not part of the low power iomux controller,
so move it under the normal iomuxc node.

Fixes: 184f39b5 ("ARM: dts: imx7d-sdb: Add GPIO expander node")
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>