clk: samsung: Drop useless alias in Exynos5420 clk driver

Drop clkdev alias for "mout_aclk400_mscl" clock. It was not used at all
and it was probably committed by accident.

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