Don't cast |OPENSSL_malloc|/|OPENSSL_realloc| result.

C has implicit conversion of |void *| to other pointer types so these
casts are unnecessary. Clean them up to make the code easier to read
and to make it easier to find dangerous casts.

Change-Id: I26988a672e8ed4d69c75cfbb284413999b475464
Reviewed-on: https://boringssl-review.googlesource.com/7102
Reviewed-by: David Benjamin <davidben@google.com>

ssl/t1_enc.c

diff --git a/ssl/t1_enc.c b/ssl/t1_enc.c
index a64e9d8..216514d 100644
--- a/ssl/t1_enc.c
+++ b/ssl/t1_enc.c
@@ -373,7 +373,7 @@
 
   ssl3_cleanup_key_block(ssl);
 
-  uint8_t *keyblock = (uint8_t *)OPENSSL_malloc(key_block_len);
+  uint8_t *keyblock = OPENSSL_malloc(key_block_len);
   if (keyblock == NULL) {
     OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
     return 0;