drm/i915: Don't try to disable host RPS when this was never enabled.

Specially in GT reset case this could be triggered and try
to disable things that had never been enabled. Let's add
some protection here.

Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220902095126.373036-1-rodrigo.vivi@intel.com