bnxt_en: Don't cancel sp_task from bnxt_close_nic().

When implementing driver reset from tx_timeout in the next patch,
bnxt_close_nic() will be called from the sp_task workqueue.  Calling
cancel_work() on sp_task will hang the workqueue.

Instead, set a new bit BNXT_STATE_IN_SP_TASK when bnxt_sp_task() is running.
bnxt_close_nic() will wait for BNXT_STATE_IN_SP_TASK to clear before
proceeding.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index a8b6881..f199f4c 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -927,6 +927,7 @@
 
 	unsigned long		state;
 #define BNXT_STATE_OPEN		0
+#define BNXT_STATE_IN_SP_TASK	1
 
 	struct bnxt_irq	*irq_tbl;
 	u8			mac_addr[ETH_ALEN];