tee_ree_fs: avoid race condition between fh usage/closing
tee_ree_fs: avoid race condition between fh usage/closing

It is possible that one core will call ree_fs_close_primitive()
while another is calling ree_fs_read_primitive(). This patch
prevents this by putting ree_fs_close_primitive under mutex.

Signed-off-by: Volodymyr Babchuk <07adff7e050dc3230ac0b7d9c296bbb62f4ecc95@gmail.com>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os