Fix pub_key comment in dh.h.

(Imported from upstream's 602af7d01da82dc6c45946572f531bcbe9ebbf47.)

Change-Id: I17cc0bfaf2d9954aafae9da30d2d37a97101f330
Reviewed-on: https://boringssl-review.googlesource.com/5691
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/dh.h b/include/openssl/dh.h
index 0174f07..75df632 100644
--- a/include/openssl/dh.h
+++ b/include/openssl/dh.h
@@ -235,7 +235,7 @@
 
   BIGNUM *p;
   BIGNUM *g;
-  BIGNUM *pub_key;  /* g^x */
+  BIGNUM *pub_key;  /* g^x mod p */
   BIGNUM *priv_key; /* x */
 
   /* priv_length contains the length, in bits, of the private value. If zero,