function_graph: Remove the unused variable func

Variable func is not effectively used, so delete it.

kernel/trace/trace_functions_graph.c:925:16: warning: variable ‘func’ set but not used.

This happened because the variable "func" which came from "call->func" was
replaced by "ret_func" coming from "graph_ret->func" but "func" wasn't
removed after the replacement.

Link: https://lore.kernel.org/20250307021412.119107-1-jiapeng.chong@linux.alibaba.com
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=19250
Fixes: ff5c9c576e ("ftrace: Add support for function argument to graph tracer")
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

kernel/trace/trace_functions_graph.c

@@ -922,7 +922,6 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 	struct ftrace_graph_ent *call;
 	unsigned long long duration;
 	unsigned long ret_func;
-	unsigned long func;
 	int args_size;
 	int cpu = iter->cpu;
 	int i;
@@ -933,8 +932,6 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 	call = &entry->graph_ent;
 	duration = ret_entry->rettime - ret_entry->calltime;
 
-	func = call->func + iter->tr->text_delta;
-
 	if (data) {
 		struct fgraph_cpu_data *cpu_data;