csh: Remove hardlink /.cshrc

Remove this historical artifact.
csh will try to use /.csrch if the user has no home directory defined which
is rather unlikely (To be exact if the concatenation of $HOME and "/.cshrc"
fail which is the same thing).

Also, with this change pkg will happily handle 3way merge for /root/.cshrc

Differential Revision: https://reviews.freebsd.org/D45382
Reviewed by: emaste, imp
Sponsored by: Beckhoff Automation GmbH & Co. KG