[AVR32] Correct misspelled CONFIG_BLK_DEV_INITRD variable.

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

arch/avr32/kernel/setup.c

@@ -313,7 +313,7 @@ __tagtable(ATAG_MEM, parse_tag_mem);
 
 static int __init parse_tag_rdimg(struct tag *tag)
 {
-#ifdef CONFIG_INITRD
+#ifdef CONFIG_BLK_DEV_INITRD
 	struct tag_mem_range *mem = &tag->u.mem_range;
 	int ret;