radv: don't set sx_blend_opt_epsilon for V_028C70_COLOR_10_11_11

radv: don't set sx_blend_opt_epsilon for V_028C70_COLOR_10_11_11

Matches radeonsi and PAL. From PAL:
// 1 is recommended, but doesn't provide sufficient precision

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4394
Fixes: ed946381564 ("radv: Enable RB+ where possible.")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9427>