[ARM] 5595/1: ep93xx: missing header in dma-m2p.c

<linux/io.h> was getting included by <mach/ts72xx.h>, is should be
included by this file.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>