Fix quoting problem (preboot setting) in many board config files.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/include/configs/v37.h b/include/configs/v37.h
index 0407253..47851c2 100644
--- a/include/configs/v37.h
+++ b/include/configs/v37.h
@@ -58,7 +58,7 @@
 #endif
 
 #define	CONFIG_CLOCKS_IN_MHZ	1	/* clocks passsed to Linux in MHz */
-#define CONFIG_PREBOOT	"echo;echo Type \"run flash_nfs\" to mount root filesystem over NFS;echo"
+#define CONFIG_PREBOOT	"echo;echo Type \\\"run flash_nfs\\\" to mount root filesystem over NFS;echo"
 
 #undef	CONFIG_BOOTARGS