drm/i915: Fix wrong condition in bxt_set_cdclk for DG2

By my own mistake, after adding !IS_DG2 into wrong branch,
bxt_set_cdclk started to execute code intended for platforms
gen < 11, which is wrong.
Move IS_DG2 check to better place.

Fixes: ceb0cc3b

 ("drm/i915: Communicate display power demands to pcode")
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230506144217.26075-1-stanislav.lisovskiy@intel.com