spl: Kconfig: Record proper dependency for SPL_ATF

ATF support was all the time based on FIT image support but this dependency
is not recorded anywhere.
For !SPL_FIT && SPL_ATF there is compilation error:
common/spl/spl.c: In function 'board_init_r':
common/spl/spl.c:689:26: error: 'struct spl_image_info' has no member named 'fdt_addr'
  689 |   spl_fixup_fdt(spl_image.fdt_addr);

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