i.MX25: fix get_rate_otg to return the correct value

usb drivers need to get the right value for otg clock so
calculate and return it
Signed-off-by: NEric Bénard <eric@eukrea.com>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx25/clock.c

@@ -131,7 +131,10 @@ static unsigned long get_rate_lcdc(struct clk *clk)
 
 static unsigned long get_rate_otg(struct clk *clk)
 {
-	return 48000000; /* FIXME */
+	unsigned long cctl = readl(CRM_BASE + CCM_CCTL);
+	unsigned long rate = get_rate_upll();
+
+	return (cctl & (1 << 23)) ? 0 : rate / ((0x3F & (cctl >> 16)) + 1);
 }
 
 static int clk_cgcr_enable(struct clk *clk)