gpu: nvgpu: gm20b: dynamically detect priv security for secure boot of falcon

gpu: nvgpu: gm20b: dynamically detect priv security for secure boot of falcon

based on the config setting and fuse secure no non secure boot is done

Change-Id: I5937ba945c5a3a86f72e0f2a9078fcde01977137
Signed-off-by: Vijayakumar <vsubbu@nvidia.com>
Reviewed-on: http://git-master/r/487684
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>