mei: fix undefined wd symbols when MEI_ME is not set

Currently watchdog client is compiled with MEI and not
with MEI_ME

Fixes error:
When CONFIG_WATCHDOG is not enabled:

ERROR: "watchdog_unregister_device" [drivers/misc/mei/mei.ko] undefined!
ERROR: "watchdog_register_device" [drivers/misc/mei/mei.ko] undefined
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/Kconfig

 config INTEL_MEI
 	tristate "Intel Management Engine Interface"
-	depends on X86 && PCI
+	depends on X86 && PCI && WATCHDOG_CORE
 	help
 	  The Intel Management Engine (Intel ME) provides Manageability,
 	  Security and Media services for system containing Intel chipsets.