linux-wandboard

MLK-16124 clk: imx: clk-gate-scu: Replace enable/disable with prepare/unprepare

enable/disable are not allowed to sleep.
For clk_gate3_scu these functions use calls into scfw that may sleep.
Move this functionality into prepare/unprepare to avoid that.

Patch also adds is_prepared callback.

Signed-off-by: Adriana Reus <adriana.reus@nxp.com>