UPSTREAM: lib/test_stackinit: Fix static initializer test

The static initializer test got accidentally converted to a dynamic
initializer. Fix this and retain the giant padding hole without using
an aligned struct member.

Bug: 254441685
Fixes: 50ceaa95ea09 ("lib: Introduce test_stackinit module")
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210723221933.3431999-2-keescook@chromium.org


(cherry picked from commit f9398f15605a50110bf570aaa361163a85113dd1)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I4829d109eed03f2d16f1d544fe0f94296d3c8927