iommu: msm: fix secure fault handler debug logs

Present debug log mechanism of secure context bank fault
handler doesn't behave well when it tries to obtain
register dumps from secure environment and fails to get a
sane response.

It is observed that the secure environment doesn't fill up
the register dump structure passed by the kernel correctly.
This leads to secure fault handler constantly dumping
default initialized values for these register making no
sense.

This patch intends to address this issue and fixes
following.

   * initialize dump holding structure and response variable
     to 0
   * return IRQ_NONE and do not proceed if secure
     environment response is 0 length
   * replace incorrect CB register address prints by
     actual context numbers and register offsets.

Change-Id: I07f329fd5dcb4fc56f7bb9a6dc182b73b806005c
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>