msm: VPU: Add additional features for firmware logging

Added feature to get and set firmware logging level dynamically in order
to output only the types of logs that are of interest (for example,
outputting error only messages). Added an atomic counter to only allow
one user thread to access firmware logs at a time. Previously, a crash
could occur if two or more user threads try and read firmware logs
simultaneously.

Change-Id: Ia73153214e161da9392d4357f785e0cbd0d01071
Signed-off-by: Mohammed Sardar <msardar@codeaurora.org>