drm/i915: sseu: Move sseu_dev_status to i915_drv.h

drm/i915: sseu: Move sseu_dev_status to i915_drv.h

The data in this struct is provided both by getting the
slice/subslice/eu features available on a given platform and the actual
runtime state of these same features which depends on the HW's current
power saving state.

Atm members of this struct are duplicated in sseu_dev_status and
intel_device_info. For clarity and code reuse we can share one struct
for both of the above purposes. This patch only moves the struct to the
header file, the next patch will convert users of intel_device_info to
use this struct too.

Instead of unsigned int u8 is used now, which is big enough and is used
anyway in intel_device_info.

No functional change.

v2:
- s/stat/sseu/ based on the new struct name (Ben)

Reviewed-by: Robert Bragg <robert@sixbynine.org> (v1)
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com> (v1)
Tested-by: Ben Widawsky <benjamin.widawsky@intel.com> (v1)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1472659987-10417-2-git-send-email-imre.deak@intel.com