arm: zynq: Enable SPL_DM_SEQ_ALIAS for all Zynq configs

This feature is required in SPL to enable support for loading from SPI
flash when the device is booted from QSPI.

Signed-off-by: Nathan Rossi <nathan@nathanrossi.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>