[SUNRPC]: svc_{get,put}nl()

* add svc_getnl():
	Take network-endian value from buffer, convert to host-endian
	and return it.
* add svc_putnl():
	Take host-endian value, convert to network-endian and put it
	into a buffer.
* annotate svc_getu32()/svc_putu32() as dealing with network-endian.
* convert to svc_getnl(), svc_putnl().

[AV: in large part it's a carved-up Alexey's patch]

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>