configs: ls1012a: Unset ENV_ADDR value

configs: ls1012a: Unset ENV_ADDR value

LS1012A-FRWY and LS1012A-RDB crashes in flash environment when
CONFIG_ENV_ADDR value is set. Unset the config value in *_tfa_defconfig*
to resolve booting crash.

Following crash is observed:
    Using SERDES1 Protocol: 13576 (0x3508)
    "Synchronous Abort" handler, esr 0x96000006
    elr: 00000000820452c0 lr : 0000000082013f54 (reloc)
    elr: 00000000b7b932c0 lr : 00000000b7b61f54
    x0 : 0000000000000000 x1 : 000000007604e004
    x2 : 0000000000000001 x3 : 0000000000000000
    ...
    Code: 54ffff80 9100c000 17fffff7 f9402241 (3860c820)
    Resetting CPU ...

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>