dynamic-layers/meta-mender-tegra: update Nano flash layouts

Update the Mender custom flash layouts for SPI flash-equipped
Nanos to restore the missing EKS and BMP partitions and relocate/
resize the UBENV partition

- LNX partition is reduced in size by 32KiB
- UBENV partition is relocated to 0x3E0000 and
  reduced to 64KiB

with this layout, we can fit the full complement of boot partitions
that L4T expects (including the "optional" ones) and have a redundant
U-Boot environment with 32KiB per copy.

Signed-off-by: Matt Madison <matt@madison.systems>