arm64: zynqmp: Fix psu_init* external functions

In older vivado version some psu_init* files didn't contain
mask*() which were missing.

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

board/xilinx/zynqmp/xil_io.h

@@ -33,12 +33,9 @@ int Xil_In32(unsigned long addr)
 	return readl(addr);
 }
 
-void mask_delay(u32 delay);
 void usleep(u32 sleep)
 {
 	udelay(sleep);
 }
-int mask_poll(u32 add, u32 mask);
-int mask_pollOnValue(u32 add, u32 mask, u32 value);
 
 #endif /* XIL_IO_H */