clk: mediatek: clk-gate: Shrink by adding clockgating bit check helper

clk: mediatek: clk-gate: Shrink by adding clockgating bit check helper

Add a clockgating bit check helper and use it in functions
mtk_cg_bit_is_cleared(), mtk_cg_bit_is_set() to shrink the
file size.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220103143712.46675-1-angelogioacchino.delregno@collabora.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>