iommu: msm: make context bank register dumping more generic

Make the function that prints out context bank registers more generic
so that it can be used without requiring access to the context bank
registers. Dumping secure context bank registers, for example, has to
be done offline (we can't access the secure context bank registers
from Linux).

Change-Id: Ide79595cea509d8c8e24d032a62dc0db7424f3b4
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>