taoshan: drop custom twrpgraphics.c

Not needed...

Change-Id: Ia0e0c6c6aa8ee0306070c9b72711fd7da006e4b4
taoshan: nuke custom CWM graphics

Test build (works):
https://s.basketbuild.com/dl/devs?dl=Olivier/taoshan/boot.img

Change-Id: I9bb2f51b35af09dcbcb29f63366cc114c9106389