msm: mink: Send full buffer size to TZ for smcinvoke

Currently, smcinvoke driver sends actual content size instead of
size of actual buffer. As per new requirement, TZ needs full
buffer size.

Change-Id: I9e051d8825ff753f801155d1ea941034fa5e1e12
Signed-off-by: Dinesh K Garg <dineshg@codeaurora.org>