iio: core: organize buffer file-ops in the order defined in the struct

The change is mostly cosmetic. This organizes the order of assignment of
the members of 'iio_buffer_fileops' to be similar to the one as defined in
the 'struct file_operations' type.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201117103753.8450-1-alexandru.ardelean@analog.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>