[Intel-gfx] More fastboot bits

[Jesse Barnes]

This one adds some extra checks on top of Chris's last set:
  - check for panel fit modes when inheriting from the BIOS
  - update pfit state at pipe_set_base time

It also changes the mode set vs flip checking to include the non-fb case
(e.g. if the BIOS fb was too small for the native mode), since we might
still be able to flip in that case.

Finally, it includes a clock_get routine for ilk+.  I'd appreciate if
someone could test this out on a machine where VBIOS supports the native
panel mode, so the kernel can boot from the boot loader in the native
mode.  In that case, it should actually fastboot and avoid the whole
mode set/panel power sequence.

Thanks,
Jesse