greybus: kernel_ver.h: provide pwm_is_enabled()

In the 4.7-rc1 kernel release, PWMF_ENABLED is removed and
pwm_is_enabled() is the correct way to test if a pwm device is enabled,
so provide a version of that function that will work on all older
kernels and change the pwm.c driver to use it so that it will work on
newer kernels as well.

Tested:
	Tree now builds successfully against 3.14.y, 4.4.y, 4.5.y,
	4.6.y, and 4.7-rc2 kernels
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/kernel_ver.h

@@ -328,4 +328,11 @@ static inline void reinit_completion(struct completion *x)
 }
 #endif
 
+#ifdef PWMF_ENABLED
+static inline bool pwm_is_enabled(const struct pwm_device *pwm)
+{
+	return test_bit(PWMF_ENABLED, &pwm->flags);
+}
+#endif
+
 #endif	/* __GREYBUS_KERNEL_VER_H */

drivers/staging/greybus/pwm.c

@@ -132,7 +132,7 @@ static void gb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
 
-	if (test_bit(PWMF_ENABLED, &pwm->flags))
+	if (pwm_is_enabled(pwm))
 		dev_warn(chip->dev, "freeing PWM device without disabling\n");
 
 	gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);