Remove MAXPHYS=32768 (coming from a too large cut-n-paste), it's not needed

for dom0 kernels.

sys/arch/amd64/conf/XEN3_DOM0

@@ -1,4 +1,4 @@
-# $NetBSD: XEN3_DOM0,v 1.2 2007/11/22 16:16:43 bouyer Exp $
+# $NetBSD: XEN3_DOM0,v 1.3 2007/12/06 20:02:02 bouyer Exp $
 
 include 	"arch/amd64/conf/std.xen"
 
@@ -11,7 +11,6 @@ options 	INCLUDE_CONFIG_FILE	# embed config file in kernel binary
 maxusers	32		# estimated number of users
 
 #
-options 	MAXPHYS=32768   #xbd doesn't handle 64k transfers
 options 	DOM0OPS
 # boot messages with MPBIOS, acpi and ioapic can be quite large
 options		MSGBUFSIZE=24576