ti: am335x: Fix build when networking is disabled

When compiling without CONFIG_CLOCK_SYNTHESIZER (which is implied by
CONFIG_DRIVER_TI_CPSW for am335x_evm), exclude the network setup for
AM335x-ICEv2 to avoid link time failures:

  board/ti/am335x/board.c:683: undefined reference to `setup_clock_synthesizer'

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>

board/ti/am335x/board.c

@@ -563,8 +563,8 @@ void sdram_init(void)
 }
 #endif
 
-#if !defined(CONFIG_SPL_BUILD) || \
-	(defined(CONFIG_SPL_ETH_SUPPORT) && defined(CONFIG_SPL_BUILD))
+#if defined(CONFIG_CLOCK_SYNTHESIZER) && (!defined(CONFIG_SPL_BUILD) || \
+	(defined(CONFIG_SPL_ETH_SUPPORT) && defined(CONFIG_SPL_BUILD)))
 static void request_and_set_gpio(int gpio, char *name, int val)
 {
 	int ret;
@@ -621,8 +621,8 @@ int board_init(void)
 	gpmc_init();
 #endif
 
-#if !defined(CONFIG_SPL_BUILD) || \
-	(defined(CONFIG_SPL_ETH_SUPPORT) && defined(CONFIG_SPL_BUILD))
+#if defined(CONFIG_CLOCK_SYNTHESIZER) && (!defined(CONFIG_SPL_BUILD) || \
+	(defined(CONFIG_SPL_ETH_SUPPORT) && defined(CONFIG_SPL_BUILD)))
 	if (board_is_icev2()) {
 		int rv;
 		u32 reg;