iio: imu: adis16400: drop ifdef around CONFIG_DEBUG_FS

Use IS_ENABLED(CONFIG_DEBUG_FS) to return in case debugfs is not present.
Since this is known at compile time, it allows the compiler to drop any
unused code. Therefore no need to wrap the code with #ifdef.

While at it make adis16400_debugfs_init() void as the return code is
ignored.
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240809-dev-adis-debugfs-improv-v1-3-d3adb6996518@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/adis16400.c

@@ -202,8 +202,6 @@ enum {
 	ADIS16400_SCAN_TIMESTAMP,
 };
 
-#ifdef CONFIG_DEBUG_FS
-
 static ssize_t adis16400_show_serial_number(struct file *file,
 		char __user *userbuf, size_t count, loff_t *ppos)
 {
@@ -273,11 +271,14 @@ static int adis16400_show_flash_count(void *arg, u64 *val)
 DEFINE_DEBUGFS_ATTRIBUTE(adis16400_flash_count_fops,
 	adis16400_show_flash_count, NULL, "%lld\n");
 
-static int adis16400_debugfs_init(struct iio_dev *indio_dev)
+static void adis16400_debugfs_init(struct iio_dev *indio_dev)
 {
 	struct adis16400_state *st = iio_priv(indio_dev);
 	struct dentry *d = iio_get_debugfs_dentry(indio_dev);
 
+	if (!IS_ENABLED(CONFIG_DEBUG_FS))
+		return;
+
 	if (st->variant->flags & ADIS16400_HAS_SERIAL_NUMBER)
 		debugfs_create_file_unsafe("serial_number", 0400,
 				d, st, &adis16400_serial_number_fops);
@@ -286,19 +287,8 @@ static int adis16400_debugfs_init(struct iio_dev *indio_dev)
 				d, st, &adis16400_product_id_fops);
 	debugfs_create_file_unsafe("flash_count", 0400,
 			d, st, &adis16400_flash_count_fops);
-
-	return 0;
 }
 
-#else
-
-static int adis16400_debugfs_init(struct iio_dev *indio_dev)
-{
-	return 0;
-}
-
-#endif
-
 enum adis16400_chip_variant {
 	ADIS16300,
 	ADIS16334,