Updated related Linux Driver Refactoring

Update of the client part, related to the Linux Driver
Refactoring at https://github.com/OP-TEE/optee_linuxdriver/pull/17



Fix #16

Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (STM platform)
Tested-by: Pascal Brand <pascal.brand@linaro.org> (QEMU)
Tested-by: Cedric Chaumont <cedric.chaumont@linaro.org> (FVP)
Tested-by: Cedric Chaumont <cedric.chaumont@linaro.org> (Juno)
Signed-off-by: Cedric Chaumont <cedric.chaumont@st.com>