[A62] fix bus_id for External SD and eMMC

  print_boot_device() (board/seco/common/board_imx6.c) uses information contained in the CPU
  registers to identify the current boot device. The boot device is identified among the ones
  specified into boot_mem_dev_list; since commit f7da4b01,
  the function check if the bus id of the current boot device is equal to the one in boot_mem_dev_list;
  if this control fails, the boot device is skipped; if no boot device is identified, the boot
  device is considerd "Unknow". In order to corretly detect the boot device for A62 board we
  have to correctly specify the bus ids.

board/seco/imx6qdl_a62/imx6qdl_a62.c

@@ -116,8 +116,8 @@ static inline void disable_apx_watchdog( void ) {
 int usdhc_devno[4] = { -1, -1, 1, 0};
 
 boot_mem_dev_t boot_mem_dev_list[SECO_NUM_BOOT_DEV] = {
-	{ 0x4, 0x5, -1,   0, -1, "External SD" },
-	{ 0x6, 0x7, -1,   0, -1, "eMMC" },
+	{ 0x4, 0x5, -1,   2, -1, "External SD" },
+	{ 0x6, 0x7, -1,   3, -1, "eMMC" },
 };
 
 #ifdef CONFIG_SPL_BUILD