Add support for calculating hashes with watchdog triggering

Implement watchodg-aware variants of hash calculation functions:
- crc32_wd()
- md5_wd()
- sha1_csum_wd()
The above functions calculate the hash of the input buffer in chunks,
triggering the watchdog after processing each chunk. The chunk size
is given as a function call parameter.

Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>

include/u-boot/md5.h

@@ -20,4 +20,12 @@ struct MD5Context {
  */
 void md5 (unsigned char *input, int len, unsigned char output[16]);
 
+/*
+ * Calculate and store in 'output' the MD5 digest of 'len' bytes at 'input'.
+ * 'output' must have enough space to hold 16 bytes. If 'chunk' Trigger the
+ * watchdog every 'chunk_sz' bytes of input processed.
+ */
+void md5_wd (unsigned char *input, int len, unsigned char output[16],
+		unsigned int chunk_sz);
+
 #endif /* _MD5_H */