s390/kconfig: split the s390 base menu

Split the base menu into more descriptive categories like processor,
memory, etc. and move virtualization related entries to the
Virtualization menu.
Also select KEXEC unconditionally.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kvm/Kconfig

@@ -5,7 +5,7 @@ source "virt/kvm/Kconfig"
 
 menuconfig VIRTUALIZATION
 	def_bool y
-	prompt "Virtualization"
+	prompt "KVM"
 	---help---
 	  Say Y here to get to see options for using your Linux host to run other
 	  operating systems inside virtual machines (guests).