opkg has supported the --add-exclude option to install since 0.3.0, so use it to
implement support for PACKAGE_EXCLUDE.
(From OE-Core rev: 6cc99d48c57cb22104980d0d758540e06cb7b80d)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>