gma500: being abstracting out devices a bit more

We really want to move towards a completely abstracted interface rather
than having tons of per chip junk in the same files.

Begin with the power code which is probably the worst offender. Add a set
of methods, initialise a dev_priv->ops pointer and rip the chip specifics
out of the power code. While we are it pick up the display init bits.

So we know it's now chip specifics clean remove the psb_ naming from it.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>