ARM: dts: imx: Add missing pinctrl-names for panel on M53Menlo

The panel already contains pinctrl-0 phandle, but it is missing
the default pinctrl-names property, so the pin configuration is
ignored. Fill in the missing pinctrl-names property, so the pin
configuration is applied.

Fixes: d81765d6 ("ARM: dts: imx53: Update LCD panel node on M53Menlo")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>