board: stm32mp1: Add env_ext4_get_dev_part() and env_ext4_get_intf()

This allows to :
- select the current device to save the environment file
- select the correct EXT4 boot device instance
  and partition to save the environment file.

For EXT4, device is mmc, device instance is 0 for sdcard or 1 for eMMC.
The partition is set to "auto" to select the first partition with
bootable flag.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

board/st/stm32mp1/stm32mp1.c

@@ -19,6 +19,7 @@
 #include <asm/io.h>
 #include <asm/gpio.h>
 #include <asm/arch/stm32.h>
+#include <asm/arch/sys_proto.h>
 #include <power/regulator.h>
 #include <usb/dwc2_udc.h>
 
@@ -505,6 +506,29 @@ void board_quiesce_devices(void)
 	setup_led(LEDST_OFF);
 }
 
+#if defined(CONFIG_ENV_IS_IN_EXT4)
+const char *env_ext4_get_intf(void)
+{
+	u32 bootmode = get_bootmode();
+
+	switch (bootmode & TAMP_BOOT_DEVICE_MASK) {
+	case BOOT_FLASH_SD:
+	case BOOT_FLASH_EMMC:
+		return "mmc";
+	default:
+		return "";
+	}
+}
+
+const char *env_ext4_get_dev_part(void)
+{
+	static char *const dev_part[] = {"0:auto", "1:auto", "2:auto"};
+	u32 bootmode = get_bootmode();
+
+	return dev_part[(bootmode & TAMP_BOOT_INSTANCE_MASK) - 1];
+}
+#endif
+
 #ifdef CONFIG_SYS_MTDPARTS_RUNTIME
 
 #define MTDPARTS_LEN		256