msm8960: update safestrap common files

Change-Id: I30aeeaa3ce99dbf940481199f64dbfb5981e8a7c
move device resolution based splashscreen images to common

Change-Id: I4f1867c0f9cd5e9aed4d304deb25fdb6d512fe9d
remove generic safestrap-common makefile, its unused

Change-Id: I4988b3b37c19c81bfdbd9976129350e738ebfab3
fix inheritance order for external/safestrap

Change-Id: Ia9e8060fc84c02be33fa6436cbf2b78c86aa9538