arm64: tegra: Enable device-tree overlay support

arm64: tegra: Enable device-tree overlay support

Add the '-@' DTC option for the Jetson TX1, Jetson Nano, Jetson TX2,
Jetson TX2 NX, Jetson AGX Xavier, Jetson Xavier NX and Jetson AGX Orin
platforms. This option populates the '__symbols__' node that contains
all the necessary symbols for supporting device-tree overlays on these
platforms. These Jetson platforms have various expansion headers,
including a 40-pin GPIO header, that allow various add-on modules to be
connected and this permits users to create device-tree overlays for
these modules.

Please note that this change does increase the size of the resulting DTB
from between 30-50%. For example, with v5.17-rc1 increase in size is as
follows:

 tegra210-p2371-2180.dtb: 79580 -> 105744 bytes
 tegra210-p3450-0000.dtb: 57465 -> 81357 bytes
 tegra186-p2771-0000.dtb: 64763 -> 99553 bytes
 tegra186-p3509-0000+p3636-0001.dtb: 48078 -> 62464 bytes
 tegra194-p2972-0000.dtb: 75303 -> 111545 bytes
 tegra194-p3509-0000+p3668-0000.dtb: 74762 -> 111995 bytes
 tegra194-p3509-0000+p3668-0001.dtb: 74578 -> 111748 bytes
 tegra234-p3737-0000+p3701-0000.dtb: 11229 -> 12917 bytes

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>