drm/i915/gen9: Update i915_drpc_info debugfs for coarse pg & forcewake info

Updated the i915_drpc_info debugfs with coarse power gating & forcewake
info for Gen9.

v2: Change all IS_GEN9() by gen >= 9 (Damien)

v3: Rebase

Cc: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1467038401-8283-1-git-send-email-akash.goel@intel.com