radv: fix emitting depth bias when beginning a command buffer

If depth bias is enabled but zero values used, they were never
emitted to the command buffer because they are equal to the default
values.

Previously, they were always emitted when the bound DS attachment
changed.

This should fix some sort of Z fighting with Dota2 on all GPUs.
This also fixes a different issue (ie. some occlusion queries failures)
on GFX6 because CLEAR_STATE is not used on that chip.

Fixes: 8a47422d ("radv: do not scale the depth bias for D16_UNORM depth surfaces")
Cc: 21.1 mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <!10310>
34 jobs for !10310 with radv_fix_missing_depth_bias_emit in 9 minutes and 56 seconds (queued for 2 seconds)
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