nfscl: Move nfsrpc_destroysession into nfscommon

This patch moves nfsrpc_destroysession() into nfscommon.ko
and also modifies its arguments slightly. This will allow
the function to be called from nfsv4_sequencelookup() in
a future commit.

This patch should not result in a semantics change.

PR: 260011
(cherry picked from commit dff31ae1c59cab9437e88bfd0f2abd35ddaa98f1)