NFC: dts: st21nfcb_i2c: Fix invalid interrupts polarity.

St21nfcb has a reverse polarity compare to st21nfca.
In st21nfcb case, the irq pin is active high.
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

Documentation/devicetree/bindings/net/nfc/st21nfcb.txt

@@ -26,7 +26,7 @@ Example (for ARM-based BeagleBoard xM with ST21NFCB on I2C2):
 		clock-frequency = <400000>;
 
 		interrupt-parent = <&gpio5>;
-		interrupts = <2 IRQ_TYPE_LEVEL_LOW>;
+		interrupts = <2 IRQ_TYPE_LEVEL_HIGH>;
 
 		reset-gpios = <&gpio5 29 GPIO_ACTIVE_HIGH>;
 	};