vfs_vnops.c: Change the error return from ENOSYS to EOPNOTSUPP

When the COPY_FILE_RANGE_CLONE flag argument is provided to
copy_file_range(2), it will return failure if block cloning
is not supported by the underlying file system.

This patch changes the errno returned for this failure from
ENOSYS to EOPNOTSUPP.

Suggested by: kib
Fixes: 37b2cb5ecb0f ("vfs: Add support for file cloning to VOP_COPY_FILE_RANGE")