Don't alter any txd->srcbus or txd->dstbus values while building the
LLI list.  This allows us to see the original dma_addr_t values passed
in via the prep_memcpy() method.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>