lib: merge CRC16-CCITT into u-boot/crc.h

This merges the CRC16-CCITT headers into u-boot/crc.h to prepare for
rolling CRC16 into the hash infrastructure.  Given that CRC8, CRC32
and CRC32-C already have their prototypes in a single header file, it
seems a good idea to also include CRC16-CCITT in the same.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/common/xyzModem.c b/common/xyzModem.c
index 830fca8..e5c65b4 100644
--- a/common/xyzModem.c
+++ b/common/xyzModem.c
@@ -24,7 +24,7 @@
 #include <common.h>
 #include <xyzModem.h>
 #include <stdarg.h>
-#include <crc.h>
+#include <u-boot/crc.h>
 
 /* Assumption - run xyzModem protocol over the console port */