ChromeOS mainboards: Move more Kconfig symbols under CHROMEOS

Move the CHROMEOS dependent symbols VIRTUAL_DEV_SWITCH and
VBOOT_DYNAMIC_WORK_BUFFER under the CHROMEOS config options for the
mainboards that use them.

Change-Id: Iad126cf045cb3a312319037aff3c4b1f15f6529d
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: http://review.coreboot.org/11336
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)

src/mainboard/intel/kunimitsu/Kconfig

@@ -17,13 +17,13 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select MMCONF_SUPPORT
 	select MONOTONIC_TIMER_MSR
 	select SOC_INTEL_SKYLAKE
-	select VIRTUAL_DEV_SWITCH
 
 config CHROMEOS
 	select CHROMEOS_RAMOOPS_DYNAMIC
 	select CHROMEOS_VBNV_CMOS
 	select LID_SWITCH
 	select VBOOT_OPROM_MATTERS
+	select VIRTUAL_DEV_SWITCH
 
 config IRQ_SLOT_COUNT
 	int