stackinit: Fix comment for test_small_end

In union test_small_end, the small members are three and four.

Fixes: e71a29d ("stackinit: Add union initialization to selftests")
Closes: https://lore.kernel.org/CAMuHMdWvcKOc6v5o3-9-SqP_4oh5-GZQjZZb=-krhY=mVRED_Q@mail.gmail.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/3f8faa2d7d0d6b36571093ab0fb1fd5157abd7bb.1738593178.git.geert+renesas@glider.be
Signed-off-by: Kees Cook <kees@kernel.org>

Author: geertu

lib/stackinit_kunit.c

@@ -351,7 +351,7 @@ union test_small_start {
 	} big;
 };
 
-/* Mismatched sizes, with one and two being small */
+/* Mismatched sizes, with three and four being small */
 union test_small_end {
 	short one;
 	unsigned long two;