qcacmn: Deregister IPA handler from pdev during deinit

A htt message arrived after ipa context is freed as part of
deinitialization which was dereferenced by event handler
assigned to pdev->ipa_uc_op_cb, resulting in crash.
To fix this, during deinit pdev->ipa_uc_op_cb is deregistered
and assigned NULL before freeing up ipa context.

Change-Id: I8125cb104a538e88cda93960f7443129fabd850a
CRs-Fixed: 2793295

dp/wifi3.0/dp_ipa.h

@@ -95,6 +95,15 @@ QDF_STATUS dp_ipa_op_response(struct cdp_soc_t *soc_hdl, uint8_t pdev_id,
 QDF_STATUS dp_ipa_register_op_cb(struct cdp_soc_t *soc_hdl, uint8_t pdev_id,
 				 ipa_uc_op_cb_type op_cb, void *usr_ctxt);
 
+/**
+ * dp_ipa_register_op_cb() - Deregister OP handler function
+ * @soc_hdl - data path soc handle
+ * @pdev_id - device instance id
+ *
+ * Return: none
+ */
+void dp_ipa_deregister_op_cb(struct cdp_soc_t *soc_hdl, uint8_t pdev_id);
+
 /**
  * dp_ipa_get_stat() - Get firmware wdi status
  * @soc_hdl - data path soc handle