imx: mx6sxsabresd: add command and macros for boot m4 core

Introduce macros and command to support booting M4 core for
i.MX6SX SabreSD board.

Signed-off-by: Ye.Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>

include/configs/mx6sxsabresd.h

@@ -26,7 +26,31 @@
 #define CONFIG_MXC_UART
 #define CONFIG_MXC_UART_BASE		UART1_BASE
 
+#ifdef CONFIG_IMX_BOOTAUX
+/* Set to QSPI2 B flash at default */
+#define CONFIG_SYS_AUXCORE_BOOTDATA 0x78000000
+#define CONFIG_CMD_SETEXPR
+
+#define UPDATE_M4_ENV \
+	"m4image=m4_qspi.bin\0" \
+	"loadm4image=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${m4image}\0" \
+	"update_m4_from_sd=" \
+		"if sf probe 1:0; then " \
+			"if run loadm4image; then " \
+				"setexpr fw_sz ${filesize} + 0xffff; " \
+				"setexpr fw_sz ${fw_sz} / 0x10000; "	\
+				"setexpr fw_sz ${fw_sz} * 0x10000; "	\
+				"sf erase 0x0 ${fw_sz}; " \
+				"sf write ${loadaddr} 0x0 ${filesize}; " \
+			"fi; " \
+		"fi\0" \
+	"m4boot=sf probe 1:0; bootaux "__stringify(CONFIG_SYS_AUXCORE_BOOTDATA)"\0"
+#else
+#define UPDATE_M4_ENV ""
+#endif
+
 #define CONFIG_EXTRA_ENV_SETTINGS \
+	UPDATE_M4_ENV \
 	"script=boot.scr\0" \
 	"image=zImage\0" \
 	"console=ttymxc0\0" \