nvidia: Add GM200, GM204 and GM206 signed firmware

These NVIDIA-signed firmwares are required to enable the graphics
engine on Maxwell desktop GPUs.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

nvidia/gm206/gr/gpccs_inst.bin

+../../gm200/gr/gpccs_inst.bin
\ No newline at end of file

nvidia/gm206/gr/sw_bundle_init.bin

+../../gm200/gr/sw_bundle_init.bin
\ No newline at end of file

nvidia/gm206/gr/sw_ctx.bin

+../../gm200/gr/sw_ctx.bin
\ No newline at end of file

nvidia/gm206/gr/sw_method_init.bin

+../../gm200/gr/sw_method_init.bin
\ No newline at end of file

nvidia/gm206/gr/sw_nonctx.bin

+../../gm200/gr/sw_nonctx.bin
\ No newline at end of file