uECC_verify: fix prototype to indicate public_key

The prototype incorrectly used 'private_key' as the name
of the first argument (rather than 'public_key').  Docs and
function definition were already correctly using 'public_key'

uECC.h

diff --git a/uECC.h b/uECC.h
index dbd94de..d6ba5ad 100644
--- a/uECC.h
+++ b/uECC.h
@@ -317,7 +317,7 @@
 
 Returns 1 if the signature is valid, 0 if it is invalid.
 */
-int uECC_verify(const uint8_t *private_key,
+int uECC_verify(const uint8_t *public_key,
                 const uint8_t *message_hash,
                 unsigned hash_size,
                 const uint8_t *signature,