AP_Math: move crc8_dvb_update into crc library

libraries/AP_Math/crc.cpp

@@ -122,6 +122,15 @@ uint8_t crc8_dvb_s2_update(uint8_t crc, const void *data, uint32_t length)
     return crc;
 }
 
+// copied from AP_FETtecOneWire.cpp
+uint8_t crc8_dvb_update(uint8_t crc, const uint8_t* buf, const uint16_t buf_len)
+{
+    for (uint16_t i = 0; i < buf_len; i++) {
+        crc = crc8_dvb(buf[i], crc, 0x7);
+    }
+    return crc;
+}
+
 /*
  CRC8-Maxim implementation based on FastCRC library
  see https://github.com/FrankBoesing/FastCRC

libraries/AP_Math/crc.h

@@ -22,6 +22,7 @@ uint8_t crc_crc8(const uint8_t *p, uint8_t len);
 uint8_t crc8_dvb_s2(uint8_t crc, uint8_t a);
 uint8_t crc8_dvb(uint8_t crc, uint8_t a, uint8_t seed);
 uint8_t crc8_dvb_s2_update(uint8_t crc, const void *data, uint32_t length);
+uint8_t crc8_dvb_update(uint8_t crc, const uint8_t* buf, const uint16_t buf_len);
 uint8_t crc8_maxim(const uint8_t *data, uint16_t length);
 uint16_t crc_xmodem_update(uint16_t crc, uint8_t data);
 uint16_t crc_xmodem(const uint8_t *data, uint16_t len);