msm8909 uses the same branches as msm8916

Instead of have duplicated branches, I'm creating here the concept of
"generic platform".
For now, only msm8909 is affected by this (its generic platform being
msm8916), but this might be useful in the future, where other
platforms share the same branch.

Change-Id: Ib410bc644373e6acfab5ad449584171b948743ae