swiotlb: comment corrections

Impact: cleanup

swiotlb_map/unmap_single are now swiotlb_map/unmap_page;
trivially change all the comments to reference new names.

Also, there were some comments that should have been
referring to just plain old map_single, not swiotlb_map_single;
fix those as well.

Also change a use of the word "pointer", when what is
referred to is actually a dma/physical address.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Cc: jeremy@goop.org
Cc: ian.campbell@citrix.com
LKML-Reference: <1239199761-22886-2-git-send-email-galak@kernel.crashing.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>