Do not leave stray qword on top of stack for interrupts and exceptions
without error code. Doing so it mis-aligned the stack.

Since the only consumer of the SSE instructions with the alignment
requirements is AES-NI module, and since the FPU context cannot be
accessed in interrupts, the only situation where the alignment matter
are the compat32 syscalls, as reported in the PR.

PR: 229222
Reported and tested by: dewayne@heuristicsystems.com.au
Sponsored by: The FreeBSD Foundation
MFC after: 1 week