Fix BIST val/dit comparison in gen_tag_macros (axi_llc_tag_store)

[gm-openchip]

The original code performed a bitwise XNOR between a temporary packed struct and ram_rdata, then re-sliced the result back into a tag_data_t struct:

    assign ram_compared = tag_data_t'{val: ..., dit: ..., tag: ...} ~^ ram_rdata;
    assign bist_res[i]  = ram_compared.val & ram_compared.dit & tag_equ[i];

Per IEEE 1800-2017, ~^ on packed structs operates on the flattened bit vector. Re-slicing the result into struct fields is valid but error-prone: for single-bit fields(val, dit), I observed that even though the compilation passes, the XNOR result was consistently 0 regardless of the actual values, confirmed in simulation (ram_rdata.val == bist_pattern.val == 1, but ram_compared.val == 0).
This was putting the LLC in SPM mode, as BIST was failing.

Replaced with explicit per-field comparisons:

• tag: XNOR reduction on the tag field only, with an explicit mux on Bist vs Lookup
• val, dit: == comparison directly on the relevant struct fields

Functionally equivalent for Lookup/Flush (tag_equ unchanged), fixes BIST result accumulation in axi_llc_tag_pattern_gen.