rockchip: defconfig: puma-rk3399: sync up with SPL changes for ATF

rockchip: defconfig: puma-rk3399: sync up with SPL changes for ATF

This defconfig update makes use of the new features:
 * CONFIG_ROCKCHIP_SPL_RESERVE_IRAM is now set to 0, as there is no
   overlap between the M0 firmware and the ATF (we load this to DRAM
   and relocate it to its final location within the ATF)
 * tracks the ATF_SUPPORT -> ATF renaming

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>