README: note JetPack version for TX1, TX2
README: note JetPack version for TX1, TX2

since JetPack includes non-BSP components not
tracked with L4T version numbering.

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

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