ARM: mvebu: improve comments in coherency_ll.S

ARM: mvebu: improve comments in coherency_ll.S

This commit makes no functional change, it only improves a bit the
various code comments in mach-mvebu/coherency_ll.S, by fixing a few
typos and adding a few more details.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1400762882-10116-4-git-send-email-thomas.petazzoni@free-electrons.com
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>