ftrace: Fix improper usage of __trace_stack() function.

In kernel/trace/trace_events_trigger.c --> stacktrace_trigger() -->
__trace_stack() is not defined as per the function definition.

With commit edbaaa13a660
("tracing: Merge irqflags + preemt counter, add RT bits")
the irqflags(flags) and preemption counter(preempt_count()) are
now should be evaluated early by tracing_gen_ctx().

This patch replaces the irqflags and preemption counter
with tracing_gen_ctx().

Fixes: 5e8446e3 ("tracing: Dump stacktrace trigger to the corresponding instance")
Link: https://lore.kernel.org/r/20220723064943.16532-1-s.anandje1@gmail.com


Signed-off-by: Anand Je Saipureddy <s.anandje1@gmail.com>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>