Remove redundant layer under iomux and add grp surfix for pinmux node name
to fix below CHECK_DTB warning:
arch/arm/boot/dts/nxp/vf/vf610-colibri-eval-v3.dtb: pinctrl@40048000 (fsl,vf610-iomuxc):
Unevaluated properties are not allowed ('vf610-colibri' was unexpected)
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>