Unnecessary NULL checks.

Missed a few the last time around.

Change-Id: I42fd57566d64fa1c41cba14573742d42468cc07d
Reviewed-on: https://boringssl-review.googlesource.com/6349
Reviewed-by: Adam Langley <alangley@gmail.com>

crypto/dh/dh.c

diff --git a/crypto/dh/dh.c b/crypto/dh/dh.c
index 87a640d..ee6c9a0 100644
--- a/crypto/dh/dh.c
+++ b/crypto/dh/dh.c
@@ -129,15 +129,15 @@
 
   CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data);
 
-  if (dh->method_mont_p) BN_MONT_CTX_free(dh->method_mont_p);
-  if (dh->p != NULL) BN_clear_free(dh->p);
-  if (dh->g != NULL) BN_clear_free(dh->g);
-  if (dh->q != NULL) BN_clear_free(dh->q);
-  if (dh->j != NULL) BN_clear_free(dh->j);
-  if (dh->seed) OPENSSL_free(dh->seed);
-  if (dh->counter != NULL) BN_clear_free(dh->counter);
-  if (dh->pub_key != NULL) BN_clear_free(dh->pub_key);
-  if (dh->priv_key != NULL) BN_clear_free(dh->priv_key);
+  BN_MONT_CTX_free(dh->method_mont_p);
+  BN_clear_free(dh->p);
+  BN_clear_free(dh->g);
+  BN_clear_free(dh->q);
+  BN_clear_free(dh->j);
+  OPENSSL_free(dh->seed);
+  BN_clear_free(dh->counter);
+  BN_clear_free(dh->pub_key);
+  BN_clear_free(dh->priv_key);
   CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock);
 
   OPENSSL_free(dh);