anv,iris: L3ALLOC register replaces L3CNTLREG for gen12

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
22 jobs for !1877 with gen12-l3 in 16 minutes and 54 seconds (queued for 6 seconds)
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