lib/test_hash.c: fix warning in preprocessor symbol evaluation

Some versions of gcc don't like tests for the value of an undefined
preprocessor symbol, even in the #else branch of an #ifndef:

    lib/test_hash.c:224:7: warning: "HAVE_ARCH__HASH_32" is not defined [-Wundef]
     #elif HAVE_ARCH__HASH_32 != 1
	   ^
    lib/test_hash.c:229:7: warning: "HAVE_ARCH_HASH_32" is not defined [-Wundef]
     #elif HAVE_ARCH_HASH_32 != 1
	   ^
    lib/test_hash.c:234:7: warning: "HAVE_ARCH_HASH_64" is not defined [-Wundef]
     #elif HAVE_ARCH_HASH_64 != 1
	   ^

Seen with gcc 4.9, not seen with 4.1.2.

Change the logic to only check the value inside an #ifdef to fix this.

Fixes: 468a9428521e7d00 ("<linux/hash.h>: Add support for architecture-specific functions")
Link: http://lkml.kernel.org/r/20160829214952.1334674-4-arnd@arndb.de
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: George Spelvin <linux@sciencehorizons.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_hash.c

@@ -219,21 +219,27 @@ test_hash_init(void)
 	}
 
 	/* Issue notices about skipped tests. */
-#ifndef HAVE_ARCH__HASH_32
-	pr_info("__hash_32() has no arch implementation to test.");
-#elif HAVE_ARCH__HASH_32 != 1
+#ifdef HAVE_ARCH__HASH_32
+#if HAVE_ARCH__HASH_32 != 1
 	pr_info("__hash_32() is arch-specific; not compared to generic.");
 #endif
-#ifndef HAVE_ARCH_HASH_32
-	pr_info("hash_32() has no arch implementation to test.");
-#elif HAVE_ARCH_HASH_32 != 1
+#else
+	pr_info("__hash_32() has no arch implementation to test.");
+#endif
+#ifdef HAVE_ARCH_HASH_32
+#if HAVE_ARCH_HASH_32 != 1
 	pr_info("hash_32() is arch-specific; not compared to generic.");
 #endif
-#ifndef HAVE_ARCH_HASH_64
-	pr_info("hash_64() has no arch implementation to test.");
-#elif HAVE_ARCH_HASH_64 != 1
+#else
+	pr_info("hash_32() has no arch implementation to test.");
+#endif
+#ifdef HAVE_ARCH_HASH_64
+#if HAVE_ARCH_HASH_64 != 1
 	pr_info("hash_64() is arch-specific; not compared to generic.");
 #endif
+#else
+	pr_info("hash_64() has no arch implementation to test.");
+#endif
 
 	pr_notice("%u tests passed.", tests);