travis: Rework Freescale ARM jobs a bit

- Split the AArch64 LS10xx and LS20xx builds into their own jobs, and
  then exclude only ls1/ls2 from the catch-all.  This moves the S32V234
  job (and future i.MX8*) to the catch-all.
- Split spear out from arm926ejs and exclude freescale, not mx from that
  job.  The older Freescale i.MX boards are caught by the catch-all job
  for Freescale but now we build the non-Freescale older i.MX platforms.

Signed-off-by: Tom Rini <trini@konsulko.com>