ARM64: zynqmp: Use the same U-Boot version with/without ATF

Remove SECURE_IOU option which is not needed. U-Boot itself can detect
which EL level it is on and based on that use do platform setup.
It also simplify usage because one Kconfig entry is gone.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/include/asm/arch-zynqmp/clk.h b/arch/arm/include/asm/arch-zynqmp/clk.h
index d55bc31..b18333d 100644
--- a/arch/arm/include/asm/arch-zynqmp/clk.h
+++ b/arch/arm/include/asm/arch-zynqmp/clk.h
@@ -9,5 +9,6 @@
 #define _ASM_ARCH_CLK_H_
 
 unsigned long get_uart_clk(int dev_id);
+unsigned long zynqmp_get_system_timer_freq(void);
 
 #endif /* _ASM_ARCH_CLK_H_ */