tools/bootconfig: Print all error message in stderr

Print all error message in stderr. This also removes
unneeded tools/bootconfig/include/linux/printk.h.

Link: https://lkml.kernel.org/r/163187298106.2366983.15210300267326257397.stgit@devnote2



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