ARM: zynq: Call ps7_post_config() for SPL

If ps7_post_config() is defined call it. It is enabling for example
level shifters for PL bitstreams.

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

arch/arm/mach-zynq/spl.c

@@ -91,6 +91,21 @@ __weak void ps7_init(void)
 	 */
 }
 
+__weak int ps7_post_config(void)
+{
+	/*
+	 * This function is overridden by the one in
+	 * board/xilinx/zynq/(platform)/ps7_init_gpl.c, if it exists.
+	 */
+	return 0;
+}
+
+void spl_board_prepare_for_boot(void)
+{
+	ps7_post_config();
+	debug("SPL bye\n");
+}
+
 #ifdef CONFIG_SPL_LOAD_FIT
 int board_fit_config_name_match(const char *name)
 {