msm: ADSPRPC: Handle Null pointer De-reference

Retrieved tgid from current process instead of
mapping  for naming the minidump region.

Change-Id: I598606577c63794f495c9ca92adc951c088046be
Acked-by: Krishnaiah Tadakamalla <ktadakam@qti.qualcomm.com>
Acked-by: Gururaj Chalgeri <gchalger@qti.qualcomm.com>
Signed-off-by: Jeya R <jeyr@codeaurora.org>