ARM: imx: enable support for mx35 rtc

The i.MX35 has an RTC compatible with the i.MX31's, so enable its support even
if it's not very useful because it's not battery backed.

Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>