miniroot prototype disklabels should attempt to contain accurate

prototype information (in this case, the miniroot-building code is
completely lovecraft)

src/etc/etc.arm64/disktab

@@ -1,4 +1,4 @@
-# $OpenBSD: disktab,v 1.2 2018/09/18 13:45:09 deraadt Exp $
+# $OpenBSD: disktab,v 1.3 2019/06/28 13:28:21 deraadt Exp $
 
 # Leave nc=16; adjust size using: ns
 rdroot|ramdiskroot|RAM-disk root FS image:\
@@ -7,5 +7,5 @@ rdroot|ramdiskroot|RAM-disk root FS image:\
 	:ob#0:pb#0:oc#0:pc#16384:
 
 miniroot:\
-	:dt=rdroot:se#512:nc#9:nt#16:ns#256:\
-	:oc#0:pc#36864:
+	:dt=rdroot:se#512:nc#33:nt#16:ns#128:\
+	:oc#0:pc#67584: