target/i386: Fix exception classes for SSE/AVX instructions.

Fix the exception classes for some SSE/AVX instructions to match what is
documented in the Intel manual.

These changes are expected to have no functional effect on the behavior
that qemu implements (primarily >= 16-byte memory alignment checks). For
instance, since qemu does not implement the AC flag, there is no
difference in behavior between Exception Classes 4 and 5 for
instructions where the SSE version only takes <16 byte memory operands.
Message-Id: <20230501111428.95998-2-ricky@rzhou.org>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>