checkpatch: allow copyright statements > 80 columns

Exempt copyright statements from the 80 column rule as line-splitting or
other kinds of work-arounds decrease readability in diffs.  Identify the
copyright statement by looking for '+/* Copyright (c)', case-insensitive,
at the beginning of the line.

Change-Id: I57aafd569ff2173ca7aa3f636532060fc93b2be1
Signed-off-by: Bryan Huntsman <bryanh@codeaurora.org>