NFSv4: kill off complicated macro 'PROC'

J. Bruce Fields wrote:
...
> (This is extremely confusing code to track down: note that
> proc->pc_decode is set to nfs4svc_decode_compoundargs() by the PROC()
> macro at the end of fs/nfsd/nfs4proc.c.  Which means, for example, that
> grepping for nfs4svc_decode_compoundargs() gets you nowhere.  Patches to
> kill off that macro would be welcomed....)

the macro 'PROC' is complicated and obscure, it had better
be killed off in order to make the code more clear.

Signed-off-by: Yu Zhiguo <yuzg@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>