framebuffer: add alternative RGBA offset for SEMC 7x30

Ported from jellybean (was Change-Id: Ibf4e4069a8ebc4808a383295ebe725adcd7a45f1)

http://review.cyanogenmod.org/#/c/20403/

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: I1caa84f46022679d0346398465cc41bcf96a6ef1