qcacld-3.0: Featurize dynamic rx agggregation feature

Dynamic rx aggregation feature depends on the context
id which is obtained from the packet context block.
This context id is invalid when this feature is not
enabled, and hence can lead to out of array access/write
leading to memory corruption.

Fix this issue by not using the context id when the dynamic
rx aggregation feature is not enabled.

Change-Id: Ie551217409b0f5aa2f704f9c617949e0d42a74d0
CRs-Fixed: 2742653