imx: ventana: fix boot to SD

This fixes a regression caused by e25fbe3f
(gw_ventana: Move the DCD settings to spl code)

The clock gating must be setup prior to calling arch_cpu_init(). Without this
booting to SD (directly via eFuse or via bmode) will hang.

Cc: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>