parport: fix memory leak

After the reference count becomes 0 when put_device() is called, it will
execute the release callback where we are freeing all the allocated
memory associated with the device. We missed freeing par_dev->state.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>