crc16-ccitt: Rename file with CRC-16-CCITT implementation to crc16-ccitt.c

U-Boot CRC-16 implementation uses polynomial x^16 + x^12 + x^5 + 1 which is
not standard CRC-16 algorithm, but it is known as CRC-16-CCITT. Rename file
crc16.c to crc16-ccitt.c to reduce confusion.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/include/u-boot/crc.h b/include/u-boot/crc.h
index 52ec6a9..eba8edf 100644
--- a/include/u-boot/crc.h
+++ b/include/u-boot/crc.h
@@ -25,7 +25,7 @@
  */
 unsigned int crc8(unsigned int crc_start, const unsigned char *vptr, int len);
 
-/* lib/crc16.c - 16 bit CRC with polynomial x^16+x^12+x^5+1 (CRC-CCITT) */
+/* lib/crc16-ccitt.c - 16 bit CRC with polynomial x^16+x^12+x^5+1 (CRC-CCITT) */
 uint16_t crc16_ccitt(uint16_t crc_start, const unsigned char *s, int len);
 /**
  * crc16_ccitt_wd_buf - Perform CRC16-CCIT on an input buffer and return the