drm/xe/mcr: Avoid clobbering DSS steering

A couple copy/paste mistakes in the code that selects steering targets
for OADDRM and INSTANCE0 unintentionally clobbered the steering target
for DSS ranges in some cases.

The OADDRM/INSTANCE0 values were also not assigned as intended, although
that mistake wound up being harmless since the desired values for those
specific ranges were '0' which the kzalloc of the GT structure should
have already taken care of implicitly.

Fixes: dd08ebf6

 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240626210536.1620176-2-matthew.d.roper@intel.com
(cherry picked from commit 4f82ac61

)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>