clk: spacemit: ccu_mix: add inverted enable gate clock

clk: spacemit: ccu_mix: add inverted enable gate clock

K3 SoC has the clock IP which support to write value 0 for enabling the
clock, while write 1 for disabling it, thus the enable BIT is inverted.
So, introduce a flag to support the inverted gate clock.

Link: https://lore.kernel.org/r/20260108-k3-clk-v5-2-42a11b74ad58@gentoo.org
Signed-off-by: Yixun Lan <dlan@gentoo.org>