xen: remove XEN_PRIVILEGED_GUEST

This patch removes the Kconfig symbol XEN_PRIVILEGED_GUEST which is
used nowhere in the tree.

We do know grub2 has a script that greps kernel configuration files for
its macro. It shouldn't do that. As Linus summarized:
    This is a grub bug. It really is that simple. Treat it as one.

Besides, grub2's grepping for that macro is actually superfluous. See,
that script currently contains this test (simplified):
    grep -x CONFIG_XEN_DOM0=y $config || grep -x CONFIG_XEN_PRIVILEGED_GUEST=y $config

But since XEN_DOM0 and XEN_PRIVILEGED_GUEST are by definition equal,
removing XEN_PRIVILEGED_GUEST cannot influence this test.

So there's no reason to not remove this symbol, like we do with all
unused Kconfig symbols.

[pebolle@tiscali.nl: rewrote commit explanation.]
Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/xen/Kconfig

@@ -19,11 +19,6 @@ config XEN_DOM0
 	depends on XEN && PCI_XEN && SWIOTLB_XEN
 	depends on X86_LOCAL_APIC && X86_IO_APIC && ACPI && PCI
 
-# Dummy symbol since people have come to rely on the PRIVILEGED_GUEST
-# name in tools.
-config XEN_PRIVILEGED_GUEST
-	def_bool XEN_DOM0
-
 config XEN_PVHVM
 	def_bool y
 	depends on XEN && PCI && X86_LOCAL_APIC