dt-bindings: clock: keystone: remove unstable remark

dt-bindings: clock: keystone: remove unstable remark

Keystone clock controller bindings were marked as work-in-progress /
unstable in 2013 in commit b9e0d40c0d83 ("clk: keystone: add Keystone
PLL clock driver") and commit 7affe5685c96 ("clk: keystone: Add gate
control clock driver") Almost eleven years is enough, so drop the
"unstable" remark and expect usual ABI rules.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240224091236.10146-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>