ARM64: zynqmp: Remove unneeded timer_init function

Empty weak function is used instead.

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

board/xilinx/zynqmp/zynqmp.c

@@ -57,11 +57,6 @@ int dram_init(void)
 	return 0;
 }
 
-int timer_init(void)
-{
-	return 0;
-}
-
 void reset_cpu(ulong addr)
 {
 }