msm: vidc: Allocate memory dynamically for debugfs info_reads

Use dynamically allocated memory for constructing strings in
core_info_read & inst_info_read. This ensures that there is no
contention for a shared memory & hence avoids the requirement of
a lock. Allocate on demand, as the calls implement a debugfs
facility and hence rarely invoked. Statically allocated memory
otherwise remain idle.

Change-Id: I3ae04e0a51801a2fc901591e41e28ff6b7d198b4
Signed-off-by: Abdulla Anam <abdullahanam@codeaurora.org>