radv: remove declared but unused radv_pipeline::is_dual_src

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5837>
diff --git a/src/amd/vulkan/radv_private.h b/src/amd/vulkan/radv_private.h
index eac46ae..c19d12a 100644
--- a/src/amd/vulkan/radv_private.h
+++ b/src/amd/vulkan/radv_private.h
@@ -1697,7 +1697,6 @@
 			/* Used for rbplus */
 			uint32_t col_format;
 			uint32_t cb_target_mask;
-			bool is_dual_src;
 		} graphics;
 	};