fbdev: au1100fb: Don't store device specific data in global variables
Using global data to store device specific data is a bad pattern that
breaks if there is more than one device. So expand driver data and drop
the global variables.
While there is probably no machine that has two or more au1100fb
devices, this makes the driver a better template for new drivers and
saves some memory if there is no such bound device.
bloat-o-meter reports (for ARCH=arm allmodconfig + CONFIG_FB_AU1100=y
and ignoring the rename of the init function):