ta: os_test: return TEE_ERROR_BAD_PARAMETERS for incorrect parameters

The TEE_ERROR_BAD_PARAMETERS return code should be prefered over
TEE_ERROR_GENERIC for any failed check on the parameters.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Etienne Carriere <etienne.carriere@foss.st.com>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>