armv7/fsl-ls102xa: Workaround for DDR erratum A008514

This is a workaround for hardware erratum.
Write the value of 63b2_0042h to EDDRTQCFG will optimal the
memory controller performance.

The value: 63b2_0042h comes from the hardware team.

Signed-off-by: Yuan Yao <yao.yuan@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>