s390/unwind: always inline get_stack_pointer

Always inline get_stack_pointer() to avoid potential problems
due to compiler inlining decisions, i.e. getting stack pointer of
get_stack_pointer() itself which is later reused.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/stacktrace.h

@@ -33,7 +33,7 @@ static inline bool on_stack(struct stack_info *info,
 	return addr >= info->begin && addr + len <= info->end;
 }
 
-static inline unsigned long get_stack_pointer(struct task_struct *task,
+static __always_inline unsigned long get_stack_pointer(struct task_struct *task,
 						       struct pt_regs *regs)
 {
 	if (regs)