msm: ADSPRPC: Call find_vma with mmap_sem semaphore held

Calling find_vma() with out holding the mmap_sem semaphore is
not safe especially when an another thread could be removing
vmas from the list. Remove find_vma in places where it is
being used just for debugging purposes.

Change-Id: I1ac12410a0880d92c7301065aa656b5ad8d521cf
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>