clk/exynos5250: add sclk_hdmiphy in the list of special clocks

hdmi driver needs hdmiphy clock which is one of the parent
for hdmi mux clock. This is required while changing the parent
of mux clock.

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