ts on system RAM results in
mappings which differ in these attributes from the main system RAM
mapping.  Other architectures which similar restrictions approch this
problem in the same way - they do not permit ioremap on main system
RAM.

Make ARM behave in the same way, with a WARN_ON() such that users can
be traced and an alternative approach found.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
¾