iris: Drop XXX about checking for swizzling

iris: Drop XXX about checking for swizzling

Caio noted that this is not necessary on Gen8+:

   "Before Gen8, there was a historical configuration control field to
    swizzle address bit[6] for in X/Y tiling modes.  This was set in
    three different places: TILECTL[1:0], ARB_MODE[5:4], and
    DISP_ARB_CTL[14:13].  For Gen8 and subsequent generations, the
    swizzle fields are all reserved, and the CPU's memory controller
    performs all address swizzling modifications."

Since we don't support earlier hardware, we can skip it entirely.