alpha: align stack for page fault and user unaligned trap handlers

commit 3b35a171060f846b08b48646b38c30b5d57d17ff upstream.

do_page_fault() and do_entUna() are special because they use
non-standard stack frame layout. Fix them manually.

Cc: stable@vger.kernel.org
Tested-by: Maciej W. Rozycki <macro@orcam.me.uk>
Tested-by: Magnus Lindholm <linmag7@gmail.com>
Tested-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Maciej W. Rozycki <macro@orcam.me.uk>
Suggested-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Ivan Kokshaysky <ink@unseen.parts>
Signed-off-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>