blitter, GL blit fallback: clean up framebuffer after use

Since the framebuffer used for blits is reused, attachements must be removed
after executing the blits, otherwise, a still bound depth buffer results
in failing color blits and vice versa.

Stabelizes piglits from "fbo-generatemipmap-formats"

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/vrend_blitter.c

@@ -829,4 +829,8 @@ void vrend_renderer_blit_gl(UNUSED struct vrend_context *ctx,
       glBufferData(GL_ARRAY_BUFFER, sizeof(blit_ctx->vertices), blit_ctx->vertices, GL_STATIC_DRAW);
       glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
    }
+   glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_STENCIL_ATTACHMENT,
+                             GL_TEXTURE_2D, 0, 0);
+   glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0,
+                             GL_TEXTURE_2D, 0, 0);
 }