clk: mediatek: mt7622: Properly use CLK_IS_CRITICAL flag

clk: mediatek: mt7622: Properly use CLK_IS_CRITICAL flag

Instead of calling clk_prepare_enable() for clocks that shall stay
enabled, use the CLK_IS_CRITICAL flag, which purpose is exactly that.

Fixes: 2fc0a509e4ee ("clk: mediatek: add clock support for MT7622 SoC")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230306140543.1813621-24-angelogioacchino.delregno@collabora.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>