ARM: mxs/clock-mx28: fix up name##_set_rate

For the lcdif clock get_rate looks as follows:

	read div from HW_CLKCTRL_DIS_LCDIF.DIV
	return clk_get_rate(clk->parent) / div

with clk->parent being ref_pix_clk on my system.

ref_pix_clk's rate depends on HW_CLKCTRL_FRAC1.PIXFRAC.

The set_rate function for lcdif does:

	parent_rate = clk_get_rate(clk->parent);
	based on that calculate frac and div such that
	  parent_rate * 18 / frac / div is near the requested rate.
	HW_CLKCTRL_FRAC1.PIXFRAC is updated with frac
	HW_CLKCTRL_DIS_LCDIF.DIV is updated with div

For this calculation to be correct parent_rate needs to be
initialized not with the clock rate of lcdif's parent (i.e. ref_pix) but
that of its grandparent (i.e. ref_pix' parent == pll0_clk).

The obvious downside of this patch is that now set_rate(lcdif) changes
its parent's rate, too.  Still this is better than a wrong rate.

Acked-by: Shawn Guo <shawn.guo@freescale.com>
LAKML-Reference: 20110225084950.GA13684@S2101-09.ap.freescale.net
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>