Recent changes in usr/mdec require (substantial) growth of the ramdisk.

ok jsg kettenis, testing by kmos also

src/etc/etc.armv7/disktab

@@ -1,10 +1,10 @@
-# $OpenBSD: disktab,v 1.7 2020/04/03 23:18:36 jsg Exp $
+# $OpenBSD: disktab,v 1.8 2020/04/23 02:54:50 deraadt Exp $
 
 # Leave nc=16; adjust size using: ns
 rdroot|ramdiskroot|RAM-disk root FS image:\
-	:dt=rdroot:se#512:nc#16:nt#2:ns#496:\
-	:ta=4.2BSD:oa#0:pa#15872:fa#512:ba#4096:\
-	:ob#0:pb#0:oc#0:pc#15872:
+	:dt=rdroot:se#512:nc#16:nt#2:ns#560:\
+	:ta=4.2BSD:oa#0:pa#17920:fa#512:ba#4096:\
+	:ob#0:pb#0:oc#0:pc#17920:
 
 miniroot:\
 	:dt=rdroot:se#512:nc#9:nt#16:ns#256:\