NFS: reorder nfs4_sequence_regs to remove 8 bytes of padding on 64 bits

reorder nfs4_sequence_args to remove 8 bytes of padding on 64 bit
builds.

The size of this structure drops to 24 bytes from 32 and reduces the
text size of nfs.ko.
On my x86_64 size reports

		text       data     bss
2.6.32-rc5 	200996	   8512	    432	 209940	  33414	nfs.ko
+patch 		200884	   8512	    432	 209828	  333a4	nfs.ko

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>