ARM: mach-imx: support for DryIce RTC in i.MX53

ARM: mach-imx: support for DryIce RTC in i.MX53

Enable support for i.MX53 in addition to i.MX25 by providing a dummy clock
on i.MX53 since this one doesn't have a separate clock for internal RTC
but the driver requests one.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>