dma-direct: re-encrypt memory if dma_direct_alloc_pages() fails

If arch_dma_set_uncached() fails after memory has been decrypted, it needs
to be re-encrypted before freeing.

Fixes: fa7e2247 ("dma-direct: make uncached_kernel_address more general")
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>