staging:iio:Documentation generic_buffer.c update to new abi for buffers + misc fixes

Trivial space before newline fix incorporated.

Additional fixes related to handling of sign extension and shifted
data.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>

squash into buffer handling update.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>