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>