tegra-common.inc: add 'tegra' to MACHINEOVERRIDES
tegra-common.inc: add 'tegra' to MACHINEOVERRIDES

so we can eliminate some redundancy by using a single override
that covers all three SoCs.

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

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