v3d: mark mapped BO as initialized for valgrind

When we unsychronized map a BO, we tell Valgrind that the content is not
initialized yet.

But we forgot to mark it as defined when the map finishes, which leads to
several conditional jump or move depends on uninitialised value(s)
warnings when using Valgrind.

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Acked-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40964>

src/gallium/drivers/v3d/v3d_bufmgr.c

@@ -537,6 +537,7 @@ v3d_bo_map(struct v3d_bo *bo)
                 mesa_loge("BO wait for map failed");
                 abort();
         }
+        VG(VALGRIND_MAKE_MEM_DEFINED(map, bo->size));
 
         return map;
 }