[MIPS] Kconfig: Move some entries to appropriate menu

Currently KEXEC is in "Machine selection", SECCOMP, PM, APM are in
"Executable file formats" menu.  Move KEXEC and SECCOMP to "Kernel
type" and PM, APM to new "Power management options" menu.  Also
replace "config PM" with kernel/power/Kconfig.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>