[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.