arm:am33xx: Make dram_init call sdram_init() in some contexts

We have two contexts for booting these platforms.  One is SPL which is
roughly: reset, cpu_init_crit, lowlevel_init, s_init, sdram_init, _main,
board_init_f from SPL, ... then U-Boot loads.  The other is a
memory-mapped XIP case (NOR or QSPI) where we do not run an SPL.  In
this case we go, roughly: reset, cpu_init_crit, lowlevel_init, s_init,
_main, regular board_init_f.

In the first case s_init will set a valid gd and then be able to call
sdram_init which in many cases will need i2c (which needs a valid gd for
gd->cur_i2c_bus).  In this second case we must (and are able to and
should) defer sdram_init() into dram_init() called by board_init_f as gd
will have been set in _main and cleared in board_init_f.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/arch/arm/cpu/armv7/am33xx/emif4.c b/arch/arm/cpu/armv7/am33xx/emif4.c
index 2c67c32..a7a3e88 100644
--- a/arch/arm/cpu/armv7/am33xx/emif4.c
+++ b/arch/arm/cpu/armv7/am33xx/emif4.c
@@ -21,6 +21,10 @@
 
 int dram_init(void)
 {
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+	sdram_init();
+#endif
+
 	/* dram_init must store complete ramsize in gd->ram_size */
 	gd->ram_size = get_ram_size(
 			(void *)CONFIG_SYS_SDRAM_BASE,