arm64: zynqmp: Build psu_spl_init for SPL all the time

ZYNQMP_PSU_INIT_ENABLED specifically saying that has connection to full
U-Boot not SPL that's why build psu_spl_init for SPL all the time.

Also disable ZYNQMP_PSU_INIT_ENABLED because it ends up in situation that
psu_init() is called twice which is wrong. By default only SPL should call
it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/bf1e5d9a163f8853c7d951ad42965114ab0b1f50.1645104518.git.michal.simek@xilinx.com