msm: ADSPRPC: Embed job type in context identifier

Current context identifier doesn't hold job type. Reserve 2 bits
and embed job type in the context that is sent to DSP. Using context
DSP can differentiate synchronous and asychronous jobs.

Change-Id: Id1ec07a298ee874d212955e226bb51095456c272
Signed-off-by: Himateja Reddy <hmreddy@codeaurora.org>