Staging: iio: cdc: ad7152: Prefer using BIT macro

This patch fixes the following checkpatch.pl issue at multiple lines:

CHECK: Prefer using the BIT macro

Signed-off-by: Sumit Pundir <pundirsumit11@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>