This change does a simple 1-to-1 rename of the adis16400_core.c file. Now
that the `adis16400_buffer.c` file was removed, everything can be moved
into a single driver file.
But first, this rename.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>