chcr: remove unused variables net_device, pi, adap and cntrl

Variables adap, pi and cntrl are assigned but are never read, hence
they are redundant and can be removed.

Cleans up various clang build warnings.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>