[qca-nss-qdisc] Handling delete class for 5.4

5.4 kernel get/put_class has been replaced with find. So the reference
counting and subsequent calling of destroy class needs changes. This
has a draft of the changes.

Change-Id: I9981412c83496fdfcecd0d155843b165b3d7bb81
Signed-off-by: Subhash Kumar Katnapally <quic_skatnapa@quicinc.com>