scripts: sanitylib.py: Add support for STLINK-V3 probe

Recent ST boards embed the new ST-Link probe V3.
It is advertised as "STLINK-V3", update sanitylmib to take it
into account.
In handle function, it is proposed to treat it separately as current
"STM32 STLink" as processing might differ in next future (hla_serial
deprecation).

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>