uboot-imx

arm64: zynqmp: Enable SPL_SEPARATE_BSS by default

BSS section was all the time separated for SPL but this symbol wasn't
enabled. It is necessary to have it enabled for OF_SEPARATE
configuration where DTB is appended to u-boot with DTB.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>