The immediate in this operation is too large for ARM. GCC will
automatically rewrite it to use bic (where bic does an AND NOT). Clang,
however doesn't, and reasonably throws an error.

This change switches to using bic in the source file, thus making both
happy.

Change-Id: I958fa29b88bffeab20c6ee11660736222a2e6986
Reviewed-on: https://boringssl-review.googlesource.com/4410
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>