MIPS: Alchemy: move au1200fb global functions to platform data

au1200fb calls 3 functions which have to be defined in board code.
Fix this ugliness with the introduction of platform_data.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
Cc: linux-fbdev@vger.kernel.org
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2871/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>