ARM: Don't dump vmalloc addresses with show_data()

Commit a744f794 ("ARM: Don't dump ioremapped memory with show_data()")
attempted to have show_data() return early if an ioremapped address
was passed for dumping. Unfortunately, this does not work in general
since find_vm_area() will only return an area pointer if it is passed
the starting address of the area.

Since no API presently exists to find the start of a VM area given
an address within that area, simplify show_data() to skip dumping
all vmalloc addresses rather than just ioremapped addresses. Other
non-ioremapped vmalloc addresses are not frequently necessary for
debugging anyway, so the impact of this trade-off should be small.

The motivation for this change is the same as before. For stability
reasons, we do not want to dump addresses corresponding to memory-
mapped peripherals that may be unclocked or otherwise inaccessible.

Change-Id: I1c5ac716926b5b573f83a16896acbe257e99bf12
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>