st/xa: Fix a memory leak

Free the context after destruction.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
(cherry picked from commit 7fce3ca3)

src/gallium/state_trackers/xa/xa_context.c

@@ -91,6 +91,7 @@ xa_context_destroy(struct xa_context *r)
     }
 
     r->pipe->destroy(r->pipe);
+    free(r);
 }
 
 XA_EXPORT int