drm/i915: Hoover the IPS enable/disable calls into the pre/post update hooks

No reason the caller of the IPS pre/post update hooks should
be responsible for the actual IPS enab/disable. Just pull those
calls into the pre/post update hooks themselves. And while
at it let's adjust the function naming a bit to have a consistent
namespace.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209113526.7595-3-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>