Remove redundant length-check in |ec_wNAF_mul|.

Right now, |g_wNAF| and |p_wNAF| are of same size.

This change makes GCC's "-Werror=logical-op" happy and adds a compile-time
assertion in case the initial size of either array ever changes.

Change-Id: I29e39a7a121a0a9d016c53da6b7c25675ddecbdc
Reviewed-on: https://boringssl-review.googlesource.com/26104
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

crypto/fipsmodule/ec/wnaf.c

diff --git a/crypto/fipsmodule/ec/wnaf.c b/crypto/fipsmodule/ec/wnaf.c
index c8bdadd..7bc0bc7 100644
--- a/crypto/fipsmodule/ec/wnaf.c
+++ b/crypto/fipsmodule/ec/wnaf.c
@@ -73,6 +73,7 @@
 #include <openssl/err.h>
 #include <openssl/mem.h>
 #include <openssl/thread.h>
+#include <openssl/type_check.h>
 
 #include "internal.h"
 #include "../bn/internal.h"
@@ -250,8 +251,12 @@
   size_t wsize = window_bits_for_scalar_size(bits);
   size_t wNAF_len = bits + 1;
   size_t precomp_len = (size_t)1 << (wsize - 1);
+
+  OPENSSL_COMPILE_ASSERT(
+      OPENSSL_ARRAY_SIZE(g_wNAF) == OPENSSL_ARRAY_SIZE(p_wNAF),
+      g_wNAF_and_p_wNAF_are_different_sizes);
+
   if (wNAF_len > OPENSSL_ARRAY_SIZE(g_wNAF) ||
-      wNAF_len > OPENSSL_ARRAY_SIZE(p_wNAF) ||
       2 * precomp_len > OPENSSL_ARRAY_SIZE(precomp_storage)) {
     OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
     goto err;