pwm: imx27: Fix clock handling in pwm_imx27_apply()

pwm_imx27_apply() enables the clocks if the previous PWM state was
disabled. Given that the clocks are supposed to be left on iff the PWM
is running, the decision to disable the clocks at the end of the
function must not depend on the previous state.

Without this fix the enable count of the two affected clocks increases
by one whenever ->apply() changes from one disabled state to another.

Fixes: bd88d319 ("pwm: imx27: Unconditionally write state to hardware")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>