arm64: dts: lx2160a: remove duplicate pinmux nodes

arm64: dts: lx2160a: remove duplicate pinmux nodes

LX2160A pinmux is done in groups by various length bitfields within
configuration registers.

The pinmux nodes i2c7-scl-pins and i2c7-scl-gpio-pins are duplicates of
i2c6-scl-gpio and i2c6-scl-gpio-pins, writing to the same register and
bits.

These two i2c buses i2c6/i2c7 (IIC7/IIC8) are configured together in
register RCWSR13 bits 3-0.

Drop the duplicate node name and change references to the i2c6 node.

Fixes: 8a1365c7bbc1 ("arm64: dts: lx2160a: add pinmux and i2c gpio to support bus recovery")
Signed-off-by: Josua Mayer <josua@solid-run.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>