LF-257-02 dts: imx6ull: change the usdhc root clock to 396MHz

LF-257-02 dts: imx6ull: change the usdhc root clock to 396MHz

Due to the errata ERR010450 limit, this patch change the imx6ull
usdhc root clock to 132MHz in soc related dts file, remove all
the root clock setting in board dts file, after this patch,
SDR104/HS200 work at 132MHz, DDR50/DDR52 work at 33MHz.

(merged from commit: 1a3160ae69f725237752f65ee7bd47f5db4cfc1d)

Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Arulpandiyan Vadivel <arulpandiyan_vadivel@mentor.com>
Signed-off-by: Srikanth Krishnakar <Srikanth_Krishnakar@mentor.com>
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>