iwlwifi: pcie: fix race in Rx buffer allocator

Make sure the rx_allocator worker is canceled before running the
rx_init routine.  rx_init frees and re-allocates all rxb's pages.  The
rx_allocator worker also allocates pages for the used rxb's.  Running
rx_init and rx_allocator simultaniously causes a kernel panic.  Fix
that by canceling the work in rx_init.

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/pcie/rx.c

@@ -902,6 +902,8 @@ static int _iwl_pcie_rx_init(struct iwl_trans *trans)
 	}
 	def_rxq = trans_pcie->rxq;
 
+	cancel_work_sync(&rba->rx_alloc);
+
 	spin_lock(&rba->lock);
 	atomic_set(&rba->req_pending, 0);
 	atomic_set(&rba->req_ready, 0);