Slightly tweak some array allocations.

clang scan-build is annoyed it's not obvious the sizeof line matches the
pointer type. This is easy to fix and makes it be quiet.

Change-Id: Iec80d2a087f81179c88cae300f56d3f76b32b347
Reviewed-on: https://boringssl-review.googlesource.com/6701
Reviewed-by: Adam Langley <agl@google.com>

crypto/ec/p224-64.c

diff --git a/crypto/ec/p224-64.c b/crypto/ec/p224-64.c
index 3e90f43..e026fc4 100644
--- a/crypto/ec/p224-64.c
+++ b/crypto/ec/p224-64.c
@@ -1171,7 +1171,7 @@
       mixed = 1;
     }
     secrets = OPENSSL_malloc(num_points * sizeof(felem_bytearray));
-    pre_comp = OPENSSL_malloc(num_points * 17 * 3 * sizeof(felem));
+    pre_comp = OPENSSL_malloc(num_points * sizeof(felem[17][3]));
     if (mixed) {
       tmp_felems = OPENSSL_malloc((num_points * 17 + 1) * sizeof(felem));
     }

crypto/ec/p256-64.c

diff --git a/crypto/ec/p256-64.c b/crypto/ec/p256-64.c
index 75b1cab..32852dd 100644
--- a/crypto/ec/p256-64.c
+++ b/crypto/ec/p256-64.c
@@ -1750,7 +1750,7 @@
       mixed = 1;
     }
     secrets = OPENSSL_malloc(num_points * sizeof(felem_bytearray));
-    pre_comp = OPENSSL_malloc(num_points * 17 * 3 * sizeof(smallfelem));
+    pre_comp = OPENSSL_malloc(num_points * sizeof(smallfelem[17][3]));
     if (mixed) {
       tmp_smallfelems =
           OPENSSL_malloc((num_points * 17 + 1) * sizeof(smallfelem));