staging: omap-thermal: add documentation for omap_bandgap_read_temp

Document function which reads temperature register, depending on
bandgap device version.

Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/omap-thermal/omap-bandgap.c

@@ -109,6 +109,16 @@ static int omap_bandgap_power(struct omap_bandgap *bg_ptr, bool on)
 	return 0;
 }
 
+/**
+ * omap_bandgap_read_temp() - helper function to read sensor temperature
+ * @bg_ptr: pointer to omap_bandgap structure
+ * @id: bandgap sensor id
+ *
+ * Function to concentrate the steps to read sensor temperature register.
+ * This function is desired because, depending on bandgap device version,
+ * it might be needed to freeze the bandgap state machine, before fetching
+ * the register value.
+ */
 static u32 omap_bandgap_read_temp(struct omap_bandgap *bg_ptr, int id)
 {
 	struct temp_sensor_registers *tsr;