Add the MD5 algorithm

MD5 supoprt is turned on by defining CONFIG_MD5, the digest can be then
calculated using the md5() function -- see include/md5.h for details.
		    
Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>

include/md5.h

@@ -0,0 +1,23 @@
+/*
+ * This file was transplanted with slight modifications from Linux sources
+ * (fs/cifs/md5.h) into U-Boot by Bartlomiej Sieka <tur@semihalf.com>.
+ */
+
+#ifndef _MD5_H
+#define _MD5_H
+
+#include <linux/types.h>
+
+struct MD5Context {
+	__u32 buf[4];
+	__u32 bits[2];
+	unsigned char in[64];
+};
+
+/*
+ * Calculate and store in 'output' the MD5 digest of 'len' bytes at
+ * 'input'. 'output' must have enough space to hold 16 bytes.
+ */
+void md5 (unsigned char *input, int len, unsigned char output[16]);
+
+#endif /* _MD5_H */