Fix soft-fail on Android.

Broken by https://android-review.googlesource.com/253830, which moved
the code, but not the required defines.

Fix by removing the unnecessary #ifdef USE.../#define SECCOMP... and
using USE_SECCOMP_SOFTFAIL directly in seccomp_can_softfail().

Also adjust some formatting.

Bug: 30693739

Change-Id: I5cd5a70b0e2efd30097522b002806cd744f24256
3 files changed