vrend: simple refactor to vrend_hw_emit_framebuffer_state()

no functional change.

Signed-off-by: Ryan Neph <ryanneph@google.com>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/725>

src/vrend_renderer.c

@@ -2647,8 +2647,9 @@ static void vrend_hw_emit_framebuffer_state(struct vrend_sub_context *sub_ctx)
    sub_ctx->swizzle_output_rgb_to_bgr = 0;
    sub_ctx->needs_manual_srgb_encode_bitmask = 0;
    for (int i = 0; i < sub_ctx->nr_cbufs; i++) {
-      if (sub_ctx->surf[i]) {
       struct vrend_surface *surf = sub_ctx->surf[i];
+      if (!surf)
+         continue;
 
       /* glTextureView() is not applied to eglimage-backed surfaces, because it
        * causes unintended format interpretation errors. But a swizzle may still
@@ -2673,7 +2674,6 @@ static void vrend_hw_emit_framebuffer_state(struct vrend_sub_context *sub_ctx)
          sub_ctx->needs_manual_srgb_encode_bitmask |= 1 << i;
       }
    }
-   }
 
    glDrawBuffers(sub_ctx->nr_cbufs, buffers);
 }