video: ARM CLCD: use panel device node for panel initialization

There is no necessity to pass an endpoint device node to custom panel
initialization functions, because a child panel device node should be
sufficient, note that the existing init_panel() callback declaration from
linux/amba/clcd.h already prompts to use the panel device node here.

Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>