arm64: tegra: multiple dtb generation support

arm64: tegra: multiple dtb generation support

Single build generates multiple dtbs to support all relavant
platforms.

bug 1442711

Change-Id: I9ec37e7edf18b3c0a4b7b2d2000243afc84784c8
Reviewed-on: http://git-master/r/357363
Signed-off-by: Jong Kim <jongk@nvidia.com>
Reviewed-on: http://git-master/r/361697
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Adeel Raza <araza@nvidia.com>
Reviewed-by: Seema Khowala <seemaj@nvidia.com>
Tested-by: Seema Khowala <seemaj@nvidia.com>
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>