drm/i915: select framebuffer support automatically

drm/i915: select framebuffer support automatically

Migration helper.

The i915 driver recently added a 'depends on FB' rule to its
Kconfig entry - which silently turns off DRM_I915 if someone
has a working config but no CONFIG_FB selected, and upgrades
to the latest upstream kernel.

Norbert Preining reported this problem:

   Bug-Entry   : http://bugzilla.kernel.org/show_bug.cgi?id=12599
   Subject     : dri /dev node disappeared with 2.6.29-rc1

So change it to "select FB", which auto-selects framebuffer
support. This way the driver keeps working, regardless of
whether FB was enabled before or not.

Kconfig select's of interactive options can be problematic to
dependencies and can cause build breakages - but in this case
it's safe because it's a leaf entry with no dependencies of its
own.

( There is some minor circular dependency fallout as FB_I810
  and FB_INTEL also used 'depends on FB' constructs - update
  those to "select FB" too. )

Reported-by: Norbert Preining <preining@logic.at>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dave Airlie <airlied@linux.ie>