iio: accel: adxl355: Replace custom definitions with generic from units.h

The units.h provides MEGA and TERA. Replace custom ones.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220202173723.8678-1-andriy.shevchenko@linux.intel.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/adxl355_core.c

@@ -20,6 +20,8 @@
 #include <linux/mod_devicetable.h>
 #include <linux/of_irq.h>
 #include <linux/regmap.h>
+#include <linux/units.h>
+
 #include <asm/unaligned.h>
 
 #include "adxl355.h"
@@ -60,9 +62,6 @@
 #define ADXL355_PARTID_VAL		0xED
 #define ADXL355_RESET_CODE		0x52
 
-#define MEGA 1000000UL
-#define TERA 1000000000000ULL
-
 static const struct regmap_range adxl355_read_reg_range[] = {
 	regmap_reg_range(ADXL355_DEVID_AD_REG, ADXL355_FIFO_DATA_REG),
 	regmap_reg_range(ADXL355_OFFSET_X_H_REG, ADXL355_SELF_TEST_REG),