pwm: fsl-ftm: Make sure to unlock mutex on failure

Upon failure to enable clocks while trying to enable the PWM, make sure
to unlock the mutex that was taken to avoid a deadlock during subsequent
operations.
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Cc: Patrick Havelange <patrick.havelange@essensium.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-fsl-ftm.c

@@ -342,12 +342,12 @@ static int fsl_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (!oldstate->enabled) {
 		ret = clk_prepare_enable(fpc->clk[fpc->period.clk_select]);
 		if (ret)
-			return ret;
+			goto end_mutex;
 
 		ret = clk_prepare_enable(fpc->clk[FSL_PWM_CLK_CNTEN]);
 		if (ret) {
 			clk_disable_unprepare(fpc->clk[fpc->period.clk_select]);
-			return ret;
+			goto end_mutex;
 		}
 
 		regmap_update_bits(fpc->regmap, FTM_OUTMASK, BIT(pwm->hwpwm),