drm/i915/dg1: Update DMC_DEBUG3 register

Current DMC_DEBUG3(_MMIO(0x101090)) address is for TGL,
it is wrong for DG1. Just like commit 5bcc95ca
("drm/i915/dg1: Update DMC_DEBUG register"), correct
this issue for DG1 platform to avoid wrong register
being read.

BSpec: 49788

v2: fix "not wrong" typo. (Jani)

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220211002933.84240-1-chuansheng.liu@intel.com