drm/i915: Separate RPS and RC6 handling for BDW

drm/i915: Separate RPS and RC6 handling for BDW

This patch separates RC6 and RPS enabling for BDW.
RC6/RPS Disabling are handled through gen6 functions.
PM Programming guide recommends a sequence within forcewakes to
configure RC6, RPS and ring frequencies in sequence. With this
patch the order is still maintained.

v2: Update sequence numbers in RC6 programming and comment about
intent of reset_rps during gen8_enable_rps. (Radoslaw)

v3: Rebase.

Signed-off-by: Sagar Arun Kamble <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Reviewed-by: Radoslaw Szwichtenberg <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Acked-by: Imre Deak <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]