nfsd: move include of state.h from trace.c to trace.h

Any file which includes trace.h will need to include state.h, even if
they aren't using any state tracepoints. Ensure that we include any
headers that might be needed in trace.h instead of relying on the
*.c files to have the right ones.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>