Per nxp,imx8-jpeg.yaml, the clock-names entry is not valid.

Remove them.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Mirela Rabulea <mirela.rabulea@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>