spi: Drop duplicate dm.h inclusion

We only need to include this header once. Drop the duplicate.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/spi/mscc_bb_spi.c b/drivers/spi/mscc_bb_spi.c
index 0454410..e77447b 100644
--- a/drivers/spi/mscc_bb_spi.c
+++ b/drivers/spi/mscc_bb_spi.c
@@ -11,7 +11,6 @@
 #include <log.h>
 #include <malloc.h>
 #include <spi.h>
-#include <dm.h>
 #include <asm/gpio.h>
 #include <asm/io.h>
 #include <linux/bitops.h>