NFC: trf7970a: add TI recommended write of zero to Register 0x18

Signed-off-by: Geoff Lansberry <geoff@kuvee.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index 10842b7..26c9dbb 100644
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -1048,6 +1048,10 @@
 	if (ret)
 		goto err_out;
 
+	ret = trf7970a_write(trf, TRF7970A_NFC_TARGET_LEVEL, 0);
+	if (ret)
+		goto err_out;
+
 	usleep_range(1000, 2000);
 
 	trf->chip_status_ctrl &= ~TRF7970A_CHIP_STATUS_RF_ON;