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>

arch/avr32/boards/atstk1000/atstk1002.c

@@ -325,7 +325,7 @@ static int __init atstk1002_init(void)
 #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