Revert "checkpatch.pl: add check for Change-Id"

This reverts commit 7ebd05ef.

Our process requires Change-Id lines in our commit text while upstream
considers them to be "noise". Remove the blocking checkpatch error for
having a gerrit Change-Id line in the commit text.

Change-Id: I21c6f0e11ecd94facfc2b9a3bbfee4ed4d39609f
Signed-off-by: Ian Maund <imaund@codeaurora.org>