sched: remove unused __HAVE_THREAD_FUNCTIONS hook support

__HAVE_THREAD_FUNCTIONS could be defined by architectures wishing to
provide their own task_thread_info(), task_stack_page(),
setup_thread_stack() and end_of_stack() hooks.

Commit cf8e865 ("arch: Remove Itanium (IA-64) architecture")
removed the last upstream consumer of __HAVE_THREAD_FUNCTIONS, so change
the remaining !CONFIG_THREAD_INFO_IN_TASK && !__HAVE_THREAD_FUNCTIONS
conditionals to only check for the former case.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lkml.kernel.org/r/20240930050945.30304-2-ddiss@suse.de

Author: ddiss

include/linux/sched.h

@@ -1898,7 +1898,7 @@ extern unsigned long init_stack[THREAD_SIZE / sizeof(unsigned long)];
 
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 # define task_thread_info(task)	(&(task)->thread_info)
-#elif !defined(__HAVE_THREAD_FUNCTIONS)
+#else
 # define task_thread_info(task)	((struct thread_info *)(task)->stack)
 #endif
 

include/linux/sched/task_stack.h

@@ -33,7 +33,7 @@ static __always_inline unsigned long *end_of_stack(const struct task_struct *tas
 #endif
 }
 
-#elif !defined(__HAVE_THREAD_FUNCTIONS)
+#else
 
 #define task_stack_page(task)	((void *)(task)->stack)