i2c: imx: Fix ABBA deadlock again

Like other i2c controllers we see deadlock issues with clock prepare mutex.
In our case this came up with a clock output of a rtc connected to i2c bus.

This issue has already been fixed upstream by:
(d9a22d71) i2c: imx: avoid taking clk_prepare mutex in PM callbacks

But was reintroduced by a wrongly resolved merge conflict with this commit:
(d59c7185) MLK-11403: I2C: imx: restore pin setting for i2c

So again we keep the i2c clock prepared and only enable and disable it for
a transfer.

REFERENCE: https://github.com/nxp-imx/linux-imx/pull/21