dt-bindings: Correct the example for Exynos power domain clocks

Since commit 29e5eea0 ("ARM: EXYNOS: Get current parent clock for
power domain on/off") the "pclkN" names of "clock-names" property is not
parsed any more. The bindings and driver were updated but the example
was not. Fix the example now.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>