NFC: digital: Add a delay between poll cycles

This replaces the polling work struct with a delayed work struct and add
a 10 ms delay between 2 poll cycles. This avoids to flood the device
with 'switch off'/'switch on' commands.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/include/net/nfc/digital.h b/include/net/nfc/digital.h
index 0ae101e..506e3f6 100644
--- a/include/net/nfc/digital.h
+++ b/include/net/nfc/digital.h
@@ -220,7 +220,7 @@
 	struct list_head cmd_queue;
 	struct mutex cmd_lock;
 
-	struct work_struct poll_work;
+	struct delayed_work poll_work;
 
 	u8 curr_protocol;
 	u8 curr_rf_tech;