ARM: dts: nomadik: add interrupt-parent for clcd

The clcd device is lacking an interrupt-parent property, which makes
the interrupt unusable and shows up as a warning with the latest
dtc version:

arch/arm/boot/dts/ste-nomadik-s8815.dtb: Warning (interrupts_property): Missing interrupt-parent for /amba/clcd@10120000
arch/arm/boot/dts/ste-nomadik-nhk15.dtb: Warning (interrupts_property): Missing interrupt-parent for /amba/clcd@10120000

I looked up the old board files and found that this interrupt has
the same irqchip as all the other on-chip device, it just needs one
extra line.

Fixes: 17470b7d ("ARM: dts: add the CLCD LCD display to the NHK15")
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>