clk: imx: clk-fracn-gppll: fix mfd value

According to spec:
A value of 0 is disallowed and should not be programmed in this register

Fix to 1.

Fixes: 1b26cb8a ("clk: imx: support fracn gppll")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20220609132902.3504651-5-peng.fan@oss.nxp.com


Signed-off-by: Abel Vesa <abel.vesa@linaro.org>