drm/i915: Rename intel_enable_rc6 to intel_rc6_enabled

drm/i915: Rename intel_enable_rc6 to intel_rc6_enabled

This function gives the status of RC6, whether disabled or if
enabled then which state. intel_enable_rc6 will be used for
enabling RC6 in the next patch.

v2: Rebase.

v3: Rebase.

Signed-off-by: Sagar Arun Kamble <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Reviewed-by: Radoslaw Szwichtenberg <[email protected]> #1
Reviewed-by: Ewelina Musial <[email protected]> #1
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]