travis: Split i.MX jobs a bit more

- Split "tqc" and "technexion" out into their own jobs and exclude
  them from the catch-all jobs
- Clarify the job labels a little more.

Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Stefano Babic <sbabic@denx.de>