clk: meson: meson8b: fix the offset of vid_pll_dco's N value

Unlike the other PLLs on Meson8b the N value "vid_pll_dco" (a better
name would be hdmi_pll_dco or - as the datasheet calls it - HPLL) is
located at HHI_VID_PLL_CNTL[14:10] instead of [13:9].
This results in an incorrect calculation of the rate of this PLL because
the value seen by the kernel is double the actual N (divider) value.
Update the offset of the N value to fix the calculation of the PLL rate.

Fixes: 28b9fcd016126e ("clk: meson8b: Add support for Meson8b clocks")
Reported-by: Jianxin Pan <jianxin.pan@amlogic.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20181202214220.7715-2-martin.blumenstingl@googlemail.com

drivers/clk/meson/meson8b.c

@@ -134,7 +134,7 @@ static struct clk_regmap meson8b_vid_pll_dco = {
 		},
 		.n = {
 			.reg_off = HHI_VID_PLL_CNTL,
-			.shift   = 9,
+			.shift   = 10,
 			.width   = 5,
 		},
 		.l = {