compiler_types: Move unused static inline functions warning to W=2

Per Nathan, clang catches unused "static inline" functions in C files
since commit 6863f56 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

Linus said:

> So I entirely ignore W=1 issues, because I think so many of the extra
> warnings are bogus.
>
> But if this one in particular is causing more problems than most -
> some teams do seem to use W=1 as part of their test builds - it's fine
> to send me a patch that just moves bad warnings to W=2.
>
> And if anybody uses W=2 for their test builds, that's THEIR problem..

Here is the change to bump the warning from W=1 to W=2.

Fixes: 6863f56 ("kbuild: allow Clang to find unused static inline functions for W=1 build")
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20251106105000.2103276-1-andriy.shevchenko@linux.intel.com
[nathan: Adjust comment as well]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: Peter Zijlstra

include/linux/compiler_types.h

@@ -250,10 +250,9 @@ struct ftrace_likely_data {
 /*
  * GCC does not warn about unused static inline functions for -Wunused-function.
  * Suppress the warning in clang as well by using __maybe_unused, but enable it
- * for W=1 build. This will allow clang to find unused functions. Remove the
- * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings.
+ * for W=2 build. This will allow clang to find unused functions.
  */
-#ifdef KBUILD_EXTRA_WARN1
+#ifdef KBUILD_EXTRA_WARN2
 #define __inline_maybe_unused
 #else
 #define __inline_maybe_unused __maybe_unused