tracing: Use IS_ERR() check for return value of tracing_init_dentry()

tracing_init_dentry() will soon return NULL as a valid pointer for the
top level tracing directroy. NULL can not be used as an error value.
Instead, switch to ERR_PTR() and check the return status with
IS_ERR().

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --cc kernel/trace/ftrace.c
Simple merge

diff --cc kernel/trace/trace.c
Simple merge

diff --cc kernel/trace/trace_events.c
Simple merge

diff --cc kernel/trace/trace_functions_graph.c
Simple merge

diff --cc kernel/trace/trace_kprobe.c
Simple merge

diff --cc kernel/trace/trace_printk.c
Simple merge

diff --cc kernel/trace/trace_stack.c
Simple merge

diff --cc kernel/trace/trace_stat.c
Simple merge

diff --cc kernel/trace/trace_uprobe.c
Simple merge