Staging: iio: Documentation: Simplify error handling.

This also has the nice effect of removing of a temporary variable from stack and
fixes the following checkpatch.pl warning:
WARNING: Missing blank line after declarations.

Signed-off-by: Heena Sirwani <heenasirwani@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>