x11/nvidia-driver: fix build 304 and 340 after "Move manpages to share/man"
sed: /usr/ports/x11/nvidia-driver-340/work/NVIDIA-FreeBSD-x86_64-340.108/nvml/man/Makefile: No such file or directory
- Error code 1
Approved by: arrowd (mentor)
Fixes: bf8a0031d97ff4c1fc019d7061085bdc38484365 "*: Move manpages to share/man"