i2c: stm32f7: Do not prepare/unprepare clock during runtime suspend/resume

In the Linux kernel, the following vulnerability has been resolved:

i2c: stm32f7: Do not prepare/unprepare clock during runtime suspend/resume

In case there is any sort of clock controller attached to this I2C bus

controller, for example Versaclock or even an AIC32x4 I2C codec, then

an I2C transfer triggered from the clock controller clk_ops .prepare

callback may trigger a deadlock on drivers/clk/clk.c prepare_lock mutex.

This is because the clock controller first grabs the prepare_lock mutex

and then performs the prepare operation, including its I2C access. The

I2C access resumes this I2C bus controller via .runtime_resume callback,

which calls clk_prepare_enable(), which attempts to grab the prepare_lock

mutex again and deadlocks.

Since the clock are already prepared since probe() and unprepared in

remove(), use simple clk_enable()/clk_disable() calls to enable and

disable the clock on runtime suspend and resume, to avoid hitting the

prepare_lock mutex.