msm: adsprpc: Fix concurrency in early wake of fastrpc

Currently is_work_done flag is checked to free the context. There
could be concurrency where is_work_done flag is set and context is
added to async queue just before checking the flag. Propagate
is_work_done status instead of checking flag directly to avoid race
condition.

Change-Id: I50d4b1d94499f07fa40608b5cf5c62ef3aeaa64b
Signed-off-by: Himateja Reddy <hmreddy@codeaurora.org>