cmd: mvebu/bubt: Correct usage of IS_ENABLED() macro

This file was using IS_ENABLED() to test for CONFIG flags but omitted
the CONFIG_ prefix and so did not work as expected.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/cmd/mvebu/bubt.c b/cmd/mvebu/bubt.c
index 5e4ffc4..6b7d9ee 100644
--- a/cmd/mvebu/bubt.c
+++ b/cmd/mvebu/bubt.c
@@ -931,7 +931,7 @@
 	size = le32_to_cpu(hdr->blocksize);
 
 	if (hdr->blockid == 0x78) { /* SATA id */
-		struct blk_desc *blk_dev = IS_ENABLED(BLK) ? blk_get_devnum_by_uclass_id(UCLASS_SCSI, 0) : NULL;
+		struct blk_desc *blk_dev = IS_ENABLED(CONFIG_BLK) ? blk_get_devnum_by_uclass_id(UCLASS_SCSI, 0) : NULL;
 		unsigned long blksz = blk_dev ? blk_dev->blksz : 512;
 		offset *= blksz;
 	}