iio: imu: adis16400: fix memory leak

commit 9c0530e898f384c5d279bfcebd8bb17af1105873 upstream.

In adis_update_scan_mode_burst, if adis->buffer allocation fails release
the adis->xfer.

Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
[krzk: backport applied to adis16400_buffer.c instead of adis_buffer.c]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>