hw/core/qdev-properties: Use qemu_strtol() in set_mac() handler

hw/core/qdev-properties: Use qemu_strtol() in set_mac() handler

The MACAddr structure contains an array of uint8_t. Previously
if a value was out of the [0..255] range, it was silently casted
and no input validation was done.
Replace strtol() by qemu_strtol() -- so checkpatch.pl won't
complain if we move this code later -- and return EINVAL if the
input is invalid.

Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-Id: <20200930164949.1425294[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>