iris: Prepare resource_get_param for DG2's clear color modifier

For some queries in iris_resource_get_param, we've been returning properties of the aux surface when information about the clear color plane was requested. For various reasons, this worked on TGL. This doesn't work on XeHP however. On that platform, the aux surface properties are zeroed (because it doesn't have an ISL surface for the CCS). This causes errors in different code paths.

These patches are originally from !14521 (merged), but have been extracted to help the upstreaming process.