As we've seen from USB and other areas[1], we need to always do runtime
checks for DMA operating on memory regions that might be remapped. This
adds vmap checks (similar to those already in USB but missing in other
places) into dma_map_single() so all callers benefit from the checking.

[1] https://git.kernel.org/linus/3840c5b78803b2b6cc1ff820100a74a092c40cbbSuggested-by: NLaura Abbott <labbott@redhat.com>
Signed-off-by: NKees Cook <keescook@chromium.org>
[hch: fixed the printk message]
Signed-off-by: NChristoph Hellwig <hch@lst.de>