avr32:portmux: fix setup for macb1

Use portd_mask instead of portc_mask to setup the pins for port D.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/arch/avr32/cpu/at32ap700x/portmux.c b/arch/avr32/cpu/at32ap700x/portmux.c
index e3e38a2..7eb42de 100644
--- a/arch/avr32/cpu/at32ap700x/portmux.c
+++ b/arch/avr32/cpu/at32ap700x/portmux.c
@@ -122,7 +122,7 @@
 		portd_mask |= (1 << 15);/* SPD	*/
 
 	/* REVISIT: Some pins are probably pure outputs */
-	portmux_select_peripheral(PORTMUX_PORT_D, portc_mask,
+	portmux_select_peripheral(PORTMUX_PORT_D, portd_mask,
 			PORTMUX_FUNC_B, PORTMUX_BUSKEEPER);
 	portmux_select_peripheral(PORTMUX_PORT_C, portc_mask,
 			PORTMUX_FUNC_B, PORTMUX_BUSKEEPER);