plat-hikey: change default console to UART3
plat-hikey: change default console to UART3

96boards community now uses UART3 as default for all SW components.
Change default for optee_os to UART3 as well to be inline with them.

Signed-off-by: Victor Chong <4aabb03bd6dd29c44a49684d87b08ac07e10b492@linaro.org>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>
Reviewed-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>

cedric-chaumont-st-dev/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,cedric-chaumont-st-dev/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,matt2048/optee_os,cedric-chaumont-st-dev/optee_os,matt2048/optee_os,Microsoft/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,Microsoft/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os