clk/exynos5420: add sclk_hdmiphy to the list of special clocks

Add sclk_hdmiphy to the list of exposed clocks. This is required
by hdmi driver to change the parent of hdmi clock.

Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>