ColdFire:Add mb for 5253 dram initialization

The dram initialization sequence should be in order.
This patch add mb for the dram intialization code to make
sure the compiler do not disorder the code.
Signed-off-by: NJason Jin <Jason.jin@freescale.com>

arch/m68k/include/asm/io.h

@@ -81,6 +81,8 @@
 #define outl(val, port)		out_le32((u32 *)((port)+_IO_BASE), (val))
 #endif
 
+#define mb() __asm__ __volatile__ ("" : : : "memory")
+
 extern inline void _insb(volatile u8 * port, void *buf, int ns)
 {
 	u8 *data = (u8 *) buf;

board/freescale/m5253demo/m5253demo.c

@@ -27,6 +27,7 @@
 #include <common.h>
 #include <asm/immap.h>
 #include <netdev.h>
+#include <asm/io.h>
 
 int checkboard(void)
 {
@@ -63,10 +64,12 @@ phys_size_t initdram(int board_type)
 		__asm__("nop");
 
 		mbar_writeLong(MCFSIM_DACR0, 0x0000322c);
+		mb();
 		__asm__("nop");
 
 		/* Write to this block to initiate precharge */
 		*(u32 *) (CONFIG_SYS_SDRAM_BASE) = 0xa5a5a5a5;
+		mb();
 		__asm__("nop");
 
 		/* Set RE bit in DACR */
@@ -83,6 +86,7 @@ phys_size_t initdram(int board_type)
 		__asm__("nop");
 
 		*(u32 *) (CONFIG_SYS_SDRAM_BASE + 0x800) = 0xa5a5a5a5;
+		mb();
 	}
 
 	return dramsize;