linux-ti-staging: Remove old 3.8 version
linux-ti-staging: Remove old 3.8 version

* The 3.8 version is replaced with v3.12 which has full support
  for all devices.
* As part of adding a v3.15 version cleanup the v3.8 version to
  reduce the number of kernels to latest and last stable.

Signed-off-by: Chase Maupin <5a5662f468a76e0fc4391e65fb9f536df44d7380@ti.com>
Signed-off-by: Denys Dmytriyenko <d29de71aea38aad3a87d486929cb0aad173ae612@ti.com>

smoosvi/Test4,tylerwhall/meta-ti,joelagnel/meta-ti,RedFIR/meta-ti,tylerwhall/meta-ti,tylerwhall/meta-ti,RedFIR/meta-ti,rcn-ee/meta-ti,rcn-ee/meta-ti,smoosvi/Test4,rcn-ee/meta-ti,joelagnel/meta-ti,joelagnel/meta-ti,rcn-ee/meta-ti,joelagnel/meta-ti,RedFIR/meta-ti,tylerwhall/meta-ti,RedFIR/meta-ti