tee-supplicant: cast sizeof(x) to socklen_t
tee-supplicant: cast sizeof(x) to socklen_t

Fixes compilation warnings on Android:

 optee_client/tee-supplicant/src/tee_socket.c:551:12: error: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'unsigned int' [-Werror,-Wsign-compare]
                 if (slen < sizeof(*sain))
                     ~~~~ ^ ~~~~~~~~~~~~~
 optee_client/tee-supplicant/src/tee_socket.c:561:12: error: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'unsigned int' [-Werror,-Wsign-compare]
                 if (slen < sizeof(*sain6))
                     ~~~~ ^ ~~~~~~~~~~~~~~
 optee_client/tee-supplicant/src/tee_socket.c:577:12: error: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'unsigned int' [-Werror,-Wsign-compare]
                 if (slen < sizeof(*sain))
                     ~~~~ ^ ~~~~~~~~~~~~~
 optee_client/tee-supplicant/src/tee_socket.c:587:12: error: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'unsigned int' [-Werror,-Wsign-compare]
                 if (slen < sizeof(*sain6))
                     ~~~~ ^ ~~~~~~~~~~~~~~

socklen_t may be signed or unsigned, depending on which standard is
implemented. For instance, the Single UNIX Specification V2 [1] defines
it as unsigned, while the more recent Open Group Base Specifications
Issue 7 [2] does not mention signedness.

Therefore, cast sizeof(x) to socklen_t to avoid any sign mismatch.

Link: [1] http://pubs.opengroup.org/onlinepubs/7908799/xns/syssocket.h.html
Link: [2] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_socket.h.html
Signed-off-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>
Reported-by: Angela Stegmaier <0b9c9dcdc4e415fb0f73f540bab597a22cb131da@ti.com>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

prime-zeng/optee_client