clk: samsung: exynos5420: Add CLK_SET_RATE_PARENT flag to mout_mau_epll_clk

This allows changing the EPLL output frequency through the audio subsystem
clock tree leaf clocks. This change is needed to support audio on the HDMI
interface on Peach-Pi(t) Chromebook.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>