ARM: Don't dump ioremapped memory with show_data()

Memory-mapped IO address spaces cannot be safely dumped at will.
Some addresses may not be available (clocked, powered) at all times,
and may result in hangs or bus decode errors if accessed. Other
registers that are accessible may have read side-effects, and dumping
them may have adverse affects on stability or the functionality of
the affected peripheral.

Be safe, and skip dumping such addresses altogether.

Change-Id: I4cfa75f027ededf841a0240715af0db385857cbe
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>