qseecom: don't release ion share memory if scm_call unload TA failed

If a scm_call request to shutdown a TA fails, the TA is not shut down
and still in use, and the resources aren't necessarily leaked. Since
shared memory are still locked in this situation, ion shared memory
cannot be released, otherwise XPU violation occurs. Only need to
release shared memory if TA is unloaded success or that TA cannot
be found

Change-Id: I971485fb541193f77960cc7ca14b5b09de938a43
Signed-off-by: Zhen Kong <zkong@codeaurora.org>