msm: smd_pkt: catch possible array out of bounds accesses

Check to see that the device timeout that is being accessed is a valid
device instead of always assuming we get a valid device, and thus prevent
an array out of bounds access.

Change-Id: I9690bede1820b9920594e3533c14b8a5c20b337f
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>