Without |EC_POINTs_mul|, there's never more than one variable point
passed to a |EC_METHOD|'s |mul| method. This allows them to be
simplified considerably. In this commit, the p256-x86_64 implementation
has been simplified to eliminate the heap allocation and looping
related that was previously necessary to deal with the possibility of
there being multiple input points. The other implementations were left
mostly as-is; they should be similarly simplified in the future.
Change-Id: I70751d1d5296be2562af0730e7ccefdba7a1acae
Reviewed-on: https://boringssl-review.googlesource.com/6493
Reviewed-by: Adam Langley <agl@google.com>
f3376ace43