qcacmn: Check target ready before accessing registers on qca6750

Before accessing any register on chip 6750, check if target is
ready or not.

Do not allow register access if target is not ready.

Change-Id: I41a604d04e861c97bdd676998222ccecbf12fd5a
CRs-Fixed: 2688920

hif/inc/hif.h

@@ -1516,6 +1516,21 @@ void hif_srng_init_phase(struct hif_opaque_softc *hif_ctx,
 }
 #endif /* FORCE_WAKE */
 
+#ifdef HIF_IPCI
+/**
+ * hif_shutdown_notifier_cb - Call back for shutdown notifier
+ * @ctx: hif handle
+ *
+ * Return:  None
+ */
+void hif_shutdown_notifier_cb(void *ctx);
+#else
+static inline
+void hif_shutdown_notifier_cb(void *ctx)
+{
+}
+#endif /* HIF_IPCI */
+
 #ifdef HIF_CE_LOG_INFO
 /**
  * hif_log_ce_info() - API to log ce info