Revert "[ARM] pxa: remove now unnecessary dma_needs_bounce()"

This reverts commit 4fa5518c, which causes a compilation regression for
IXP4xx platforms.

Reported-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>