Tidy up ARMSOCMapMem() & ARMSOCUnmapMem()

ARMSOCMapMem() & ARMSOCUnmapMem() are badly named, trivial, static and
only called once so have been removed and merged into their calling
functions, ARMSOCInitScreen() & ARMSOCCloseScreen() respectively.
An assert has been added to check that the scanout buffer is not already
allocated when ARMSOCInitScreen() is called.

Change-Id: Ibf83e87f76a18ff9cfd5d37e1969e2034606d71b
1 file changed