When kernel_preempt not enable in configure, system bootup hangs
in sdma initialization.
This is caused by sdma initialization waiting for channel0 complete loading
script in queue, and arch_idle happens with action to disable some clocks,
if DDR clock disabled, script loading will failed and SoC hangs.
Solve it by make sure DDR clock is enabled during sdma initialization.
Signed-off-by: Zeng Zhaoming <b32542@freescale.com>
4fdaa5078c