qseecom: add mutex around qseecom_set_client_mem_param

Add mutex around qseecom_set_client_mem_param to prevent an
ioctl thread modifying and corrupting data which is being
processed by another ioctl in the other thread

Change-Id: I0cfb8afab4001c2913be693dfe44c761b9568893
Signed-off-by: Zhen Kong <zkong@codeaurora.org>