staging: slicoss: fix dma memory leak

This patch fixes a memory leak in slic_card_init. If the driver fails
to poll for an interrupt after requesting config data from the device
the dma memory is never freed.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>