sched/fair: Mark m*_vruntime() with __maybe_unused

When max_vruntime() is unused, it prevents kernel builds with clang,
`make W=1` and CONFIG_WERROR=y:

kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function]
  526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
      |                   ^~~~~~~~~~~~

Fix this by marking them with __maybe_unused (all cases for the sake of
symmetry).

See also commit 6863f56 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

Signed-off-by: Andy Shevchenko <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: andy-shev

kernel/sched/fair.c

@@ -523,7 +523,7 @@ void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
  * Scheduling class tree data structure manipulation methods:
  */
 
-static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
+static inline __maybe_unused u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 {
 	s64 delta = (s64)(vruntime - max_vruntime);
 	if (delta > 0)
@@ -532,7 +532,7 @@ static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 	return max_vruntime;
 }
 
-static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
+static inline __maybe_unused u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 {
 	s64 delta = (s64)(vruntime - min_vruntime);
 	if (delta < 0)