Hi Glenn,
Hope you downloaded L4T27.1 source code. If not, here is the link:
http://developer.nvidia.com/embedded/dlc/l4t-sources-27-1/
You need to extract kernel_src.tbz2 for kernel source.
You should find the V4L2 sensor drivers in the below folder.
kernel/kernel-4.4/drivers/media/i2c
Regards,
Rejeesh