ARM: imx35: fix ATA_DATA3 pad control address

According to the "i.MX35 (MCIMX35) Multimedia Applications Processor
Reference Manual" the correct address for the pad control register
IOMUXC_SW_PAD_CTL_PAD_ATA_DATA3 is 0x06ec, not 0x6e8.

Signed-off-by: Ryan Lortie <desrt@desrt.ca>
Acked-by: Marc Reilly <marc@cpdesign.com.au>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>