CONFIG_6xx is not available for the selected architecture x86.
Result is shown for architecture powerpc

CONFIG_6xx (not configurable)

modulename: 6xx-suspend.ko

and/or

l2cr.ko

and/or

idle_6xx.ko

configname: CONFIG_6xx

Linux/PowerPC Kernel Configuration
└─>Processor support
└─>6xx
In linux kernel since version 2.6.15 (release Date: 2006-01-02)
source code:
arch/ppc/kernel/
selects
CONFIG_PPC_HAVE_PMU_SUPPORT

depends
 or CONFIG_PPC32 |
| CONFIG_PPC_BOOK3S