Blackfin: move CONFIG_BFIN_CPU back to board config.h

This is a revert of 821ad16fa9900c as Wolfgang doesn't like the new code.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/lib/board.c b/arch/blackfin/lib/board.c
index 59a0810..2b1f78c 100644
--- a/arch/blackfin/lib/board.c
+++ b/arch/blackfin/lib/board.c
@@ -254,7 +254,7 @@
 	memset((void *)bd, 0, sizeof(bd_t));
 
 	bd->bi_r_version = version_string;
-	bd->bi_cpu = BFIN_CPU;
+	bd->bi_cpu = MK_STR(CONFIG_BFIN_CPU);
 	bd->bi_board_name = BFIN_BOARD_NAME;
 	bd->bi_vco = get_vco();
 	bd->bi_cclk = get_cclk();