xen: Kconfig: remove X86_64 depends from XEN_512GB

commit bfda93ae ("xen: Kconfig: nest Xen guest options")
accidentally re-added X86_64 as a dependency to XEN_512GB.  It was
originally removed in commit a13f2ef1 ("x86/xen: remove 32-bit Xen
PV guest support").  Remove it again.

Fixes: bfda93ae ("xen: Kconfig: nest Xen guest options")
Reported-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NJason Andryuk <jandryuk@gmail.com>
Reviewed-by: NJuergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20201216140838.16085-1-jandryuk@gmail.comSigned-off-by: NJuergen Gross <jgross@suse.com>

arch/x86/xen/Kconfig

@@ -28,7 +28,7 @@ config XEN_PV
 
 config XEN_512GB
 	bool "Limit Xen pv-domain memory to 512GB"
-	depends on XEN_PV && X86_64
+	depends on XEN_PV
 	default y
 	help
 	  Limit paravirtualized user domains to 512GB of RAM.