net: pkt: net_frag_linearize: Make consistent with net_buf_linearize

net_frag_linearize() is just a wrapper for net_buf_linearize(). As
the latter was refactored to never return error, and instead just
return actual copied length, update the former and its usages too.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
4 files changed