clk: exynos5433: Mark some clocks as critical

Some parent clocks of the Exynos5433 CMUs must be always enabled to access
any register in the given CMU or devices connected to it. For the time
being, until a proper solution based on runtime PM is applied, mark those
clocks as critical (instead of ignore unused) to prevent disabling them.

Reported-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>