jetson-xavier-nx-devkit-emmc: correct EMMC_SIZE
jetson-xavier-nx-devkit-emmc: correct EMMC_SIZE

The original value for this was copied directly
from the L4T configuration file for this module,
but was actually incorrect and disagrees with
the size information in the flash layout XML file
(which is correct).

Signed-off-by: Matt Madison <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@madison.systems>

madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra,madisongh/meta-tegra