cpufreq: imx6q: Fix clock enable balance

For changing the cpu frequency the i.MX6q has to be switched to some
intermediate clock during the PLL reprogramming. The driver tries
to be clever to keep the enable count correct but gets it wrong. If
the cpufreq is increased it calls clk_disable_unprepare twice
on pll2_pfd2_396m. This puts all other devices which get their clock
from pll2_pfd2_396m into a nonworking state.

Fix this by removing the clk enabling/disabling altogether since the
clk core will do this automatically during a reparent.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>