Merged in yanqil-br/feature-multi_chan_pwm (pull request #973)

multi-channel PWM with single chan selection

Approved-by: Gregory Nutt <gnutt@nuttx.org>

include/nuttx/drivers/pwm.h

@@ -154,6 +154,9 @@ struct pwm_info_s
   uint32_t           count;     /* The number of pulse to generate.  0 means to
                                  * generate an indefinite number of pulses */
 #  endif
+#  ifdef CONFIG_PWM_MULTICHAN_SELECT
+  uint8_t            chan_num;  /* Selects the PWM channel number to modify */
+#endif
 #endif /* CONFIG_PWM_MULTICHAN */
 };