Defaults differ for Arm and x86, not the least because of v2 not even
being security supported on Arm.

Also drop a bogus sentence from gnttab_max_maptrack_frames, which was
presumably mistakenly cloned from gnttab_max_frames (albeit even there
what is being said is neither very precise nor very useful imo).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
---
v2: Split x86 PV and HVM.

--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -1177,7 +1177,9 @@ Specify which console gdbstub should use
 ### gnttab
 > `= List of [ max-ver:<integer>, transitive=<bool>, transfer=<bool> ]`
 
-> Default: `gnttab=max-ver:2,transitive,transfer`
+> Default (Arm): `gnttab=max-ver:1`
+> Default (x86,PV): `gnttab=max-ver:2,transitive,transfer`
+> Default (x86,HVM): `gnttab=max-ver:2,transitive`
 
 Control various aspects of the grant table behaviour available to guests.
 
@@ -1217,8 +1219,6 @@ Specify the maximum number of frames to
 maptrack array. This value is an upper boundary of the per-domain
 value settable via Xen tools.
 
-Dom0 is using this value for sizing its maptrack table.
-
 ### global-pages
     = <boolean>