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: Ia095bf268c6c1c08dfe1544280567ba4bd4661d6
Signed-off-by: Mona Hossain <mhossain@codeaurora.org>