Reset the target on disconnect
Reset the target on disconnect

We refactor the target_reset() out to call it from three places, the
third being new, and conditional on the autoreset option

Signed-off-by: Jonathan Austin <977805957f645e95b2e79f6a41933c0de1ff99a1@arm.com>

sg-/DAPLink,google/DAPLink-port,google/DAPLink-port,google/DAPLink-port,sg-/DAPLink,sg-/DAPLink,google/DAPLink-port