Add SIGTERM signal handler to also call cleanup 	When stopping st-util under Eclipse as an external tool the st-util 	receives a SIGTERM signal, and would not return the device to 	usb mass storage mode.  This change now calls cleanup in the SIGTERM handler too!!
Add SIGTERM signal handler to also call cleanup
	When stopping st-util under Eclipse as an external tool the st-util
	receives a SIGTERM signal, and would not return the device to
	usb mass storage mode.  This change now calls cleanup in the SIGTERM handler too!!

gtalusan/stlink,chaosAD/stlink,swegener/stlink,trigrass2/stlink,trigrass2/stlink,ros2/stlink,swegener/stlink,fedorcomander/stlink,ros2/stlink,chaosAD/stlink,simonjwright/stlink,12019/stlink,12019/stlink,braincorp/stlink,fedorcomander/stlink,gtalusan/stlink,simonjwright/stlink,braincorp/stlink