anv/cmd_buffer: Set the L3 atomic disable mask bit in CHICKEN3 on HSW

anv/cmd_buffer: Set the L3 atomic disable mask bit in CHICKEN3 on HSW

Without this bit set, the value in "L3 Atomic Disable" won't get applied by
the hardware so we won't properly get L3 atomic caching.

Fixes dEQP-VK.spirv_assembly.instruction.compute.opatomic.compex and 198 of
the dEQP-VK.image.atomic_operations.* tests on HSW

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>