iio: accel: adxl345: simplify measure enable

Simplify the function to enable or disable measurement. Replace the
separate decision logic and call to regmap_update_bits() by a single
call to regmap_assign_bits() taking a boolean argument directly.

This is a refactoring change and should not impact functionality.

Signed-off-by: Lothar Rubusch <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/accel/adxl345.h

···
 #define ADXL345_BW_LOW_POWER		BIT(4)
 #define ADXL345_BASE_RATE_NANO_HZ	97656250LL
 
-#define ADXL345_POWER_CTL_STANDBY	0x00
 #define ADXL345_POWER_CTL_WAKEUP	GENMASK(1, 0)
 #define ADXL345_POWER_CTL_SLEEP	BIT(2)
 #define ADXL345_POWER_CTL_MEASURE	BIT(3)

drivers/iio/accel/adxl345_core.c

···
  */
 static int adxl345_set_measure_en(struct adxl345_state *st, bool en)
 {
-	unsigned int val = en ? ADXL345_POWER_CTL_MEASURE : ADXL345_POWER_CTL_STANDBY;
-
-	return regmap_write(st->regmap, ADXL345_REG_POWER_CTL, val);
+	return regmap_assign_bits(st->regmap, ADXL345_REG_POWER_CTL,
+				  ADXL345_POWER_CTL_MEASURE, en);
 }
 
 /* tap */