am335x, guardian: set tftp_load_addr in environment

Set tftp_load_addr to 0x82000000 in MEM_LAYOUT_ENV_SETTINGS

Signed-off-by: Moses Christopher <BollavarapuMoses.Christopher@in.bosch.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210611161350.2141-5-Gireesh.Hiremath@in.bosch.com