plat-stm: fix parallel build error

Generation of out/arm32-plat-stm/core/tz.lds may occur when the directory
out/arm32-plat-stm/core does not exist yet. The command should therefore
create it.
Note: plat-vexpress is correct.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>
OP-TEE design document

- Adds documentation covering platform initalization, SMC handling, TEE
  SMC Interface, thread handling and MMU.
- Adds empty sections showing what we intend to add to the
  documentation.
- Adds yEd (http://www.yworks.com/) files and the images generated by
  the tool.

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>
Use bn_free to free big numbers

At some places of the code, some big numbers, allocated through
bn_alloc_max(), where freed using free().
They are now free using bn_free()

Signed-off-by: Pascal Brand <pascal.brand@st.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (STM platform)