blue: bt: fix exit code in case of firmware download errors

thanks to Kali-

https://github.com/CyanogenMod/android_device_sony_blue-common/commit/ac9d6c7b5ee7b9d04cc2084c78f49b7c638be8e4

Change-Id: I51d89ad1c0b2a84bb413b7d769c052069af7201f