Replace iovec-based packet assembly with direct linear copy in
queue_push_ndlc_flow(). The scatter-gather approach was creating
temporary stack variables and looping through iovecs unnecessarily
for simple header + msg + tail construction.
Scatter-gather makes sense for zero-copy I/O, not for building
new packets from scratch.
Signed-off-by: Madrajib Lab <madhabsharma94@gmail.com>
