agp_add_bridge function.  It appears to be responsible for freeing
the agp_bridge_data in the case of a failure, but it is only doing
so for some errors.

Fix it to always free the bridge data if a failure condition is
encountered.
Signed-off-by: Kevin Winchester <kjwinchester@gmail.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>