Move four functions in nfscl.ko to nfscommon.ko.

Four functions nfscl_reqstart(), nfscl_fillsattr(), nfsm_stateidtom()
and nfsmnt_mdssession() are now called from within the nfsd.
As such, they needed to be moved from nfscl.ko to nfscommon.ko so that
nfsd.ko would load when nfscl.ko wasn't loaded.

Reported by: herbert@gojira.at