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>