dt-bindings: clock: imx8qxp-lpcg: correct the example clock-names

Align with all other i.MX using the mmc controller, align
the clock-names.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>