tracing/kprobes: Use probe_kernel_read instead of probe_mem_read

Use probe_kernel_read() instead of probe_mem_read() because
probe_mem_read() is a kind of wrapper for switching memory
read function between uprobes and kprobes.

Link: http://lkml.kernel.org/r/20190222011643.3e19ade84a3db3e83518648f@kernel.org



Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>