Fixed variable name error in code example doc
Fixed variable name error in code example doc

- Changed declaration of buffer header variable in documentation
  code example to use name "buffer" instead of "header" since
  this is the name used throughout the remaining code.

raspberrypi/userland,adamheinrich/userland,JamesH65/userland,raspberrypi/userland,luked99/userland-1,kraj/userland,6by9/userland,kraj/userland,ethanol100/userland,maroviher/userland,adamheinrich/userland,gonzoua/userland,roberttidey/userland,JamesH65/userland,6by9/userland,kraj/userland,maroviher/userland,adamheinrich/userland,luked99/userland-1,gonzoua/userland,luked99/userland-1,roberttidey/userland,6by9/userland,roberttidey/userland,ethanol100/userland,maroviher/userland,ethanol100/userland,JamesH65/userland,gonzoua/userland,raspberrypi/userland