nfsd: removed unused argument in nfsd_startup_generic()

Since commit 501cb184 ("nfsd: rip out the raparms cache")
nrservs is not used in nfsd_startup_generic()

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>