constify copy_siginfo_to_user{,32}()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Git-commit: ce3959604878c1c693979ec552069dc8bdb5ccde
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[imaund@codeaurora.org: resolve merge conflicts]
Signed-off-by: Ian Maund <imaund@codeaurora.org>