msm: adsprpc: Allocate buffer taking NULL byte into consideration

When attaching to audiopd on ADSP, allocate one
extra byte for the process name so that it is
null terminated when data is copied from file
pointer in the userspace.

Change-Id: Iffb9ef5cb0198ff7cbf44d0f3be03a1c9f29a90f
Acked-by: Vishnu Karthik D <vikarthi@qti.qualcomm.com>
Signed-off-by: Jeya R <jeyr@codeaurora.org>