atstk1000: fix build breakage with BOARD_ATSTK100X_SW2_CUSTOM=y

The #ifdef surrounding the code adding the mmc controller had a typo,
causing it to be compiled even when mmc was supposed to be disabled.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
diff --git a/arch/avr32/boards/atstk1000/atstk1002.c b/arch/avr32/boards/atstk1000/atstk1002.c
index ee4c292..dfc3443 100644
--- a/arch/avr32/boards/atstk1000/atstk1002.c
+++ b/arch/avr32/boards/atstk1000/atstk1002.c
@@ -325,7 +325,7 @@
 #ifdef CONFIG_BOARD_ATSTK100X_SPI1
 	at32_add_device_spi(1, spi1_board_info, ARRAY_SIZE(spi1_board_info));
 #endif
-#ifndef CONFIG_BOARD_ATSTK1002_SW2_CUSTOM
+#ifndef CONFIG_BOARD_ATSTK100X_SW2_CUSTOM
 	at32_add_device_mci(0, MCI_PDATA);
 #endif
 #ifdef CONFIG_BOARD_ATSTK1002_SW5_CUSTOM