leds: lp55xx: use common clock framework when external clock is used

Program execution is timed with 32768Hz clock in the LP55xx family devices.
To run LED functionalities, LP55xx devices provide two options.
One is using internal clock. The other is using external clock.
This patch enables external clock detection automatically.
If external clock is not detected, then the internal clock will be used in the
LP55xx driver.

Valid clock rate is 32768Hz in LP55xx devices.

This new API is used in each LP55xx driver like LP5521 and LP5562.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

drivers/leds/leds-lp55xx-common.h

@@ -83,6 +83,7 @@ struct lp55xx_device_config {
  */
 struct lp55xx_chip {
 	struct i2c_client *cl;
+	struct clk *clk;
 	struct lp55xx_platform_data *pdata;
 	struct mutex lock;	/* lock for user-space interface */
 	int num_leds;
@@ -117,6 +118,9 @@ extern int lp55xx_read(struct lp55xx_chip *chip, u8 reg, u8 *val);
 extern int lp55xx_update_bits(struct lp55xx_chip *chip, u8 reg,
 			u8 mask, u8 val);
 
+/* external clock detection */
+extern bool lp55xx_is_extclk_used(struct lp55xx_chip *chip);
+
 /* common device init/deinit functions */
 extern int lp55xx_init_device(struct lp55xx_chip *chip);
 extern void lp55xx_deinit_device(struct lp55xx_chip *chip);