ARM: dts: Add mclk entry for Peach boards

On Peach Pit and Pi boards, the Exynos SoC XCLKOUT pin provides
master clock (mclk) to the codec. So make it a clock consumer.

Signed-off-by: Tushar Behera <tushar.b@samsung.com>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Kukjin Kim <kgene@kernel.org>