sanitycheck: add argument --pre-script

add argument --pre-script to specify a pre script. This will be
executed before device handler open serial port and invoke runner.

Currently, pre_script can only get from hardware.map file. just like:
./scripts/sanitycheck  --hardware-map xxx.map
and set pre_script in xxx.map file.

Signed-off-by: Watson Zeng <zhiwei@synopsys.com>