msm8930-common: Clean up Samsung device inheritance

* Move postrecoveryboot.sh to qcom-common
* Sort flags, update based on qcom-common flag changes
* Move building of media libs to msm8930-common
* Move QCOM_BSP to platform repos
* Move common 8930 stuff out of serrano-common to here
* Move 8930 thermald configs to msm8930-common
* Move common overlay options to qcom-common