ARM: imx: using unsigned variable for do_div

The definition of do_div uses unsigned long long
variable as its first parameter, better to pass
a u64 variable as first parameter when calling
do_div function.

Signed-off-by: Anson Huang <b20788@freescale.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>