qseecom: Remove mutex lock in load_fw API

Loading of app is stuck waiting for lock on app_access_lock
being released.  This mutex is already locked prior to invoking
load_fw.
Removing the mutex lock (already called before invoking load_fw),
in load_fw, fixes the issue with the loading getting stuck.

Change-Id: Ib43a7f5a01b5246b1f1b180380f14fb70a4c92ff
Signed-off-by: Mona Hossain <mhossain@codeaurora.org>