net: switch memcpy_fromiovec()/memcpy_fromiovecend() users to copy_from_iter()

That takes care of the majority of ->sendmsg() instances - most of them
via memcpy_to_msg() or assorted getfrag() callbacks.  One place where we
still keep memcpy_fromiovecend() is tipc - there we potentially read the
same data over and over; separate patch, that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc include/linux/skbuff.h
Simple merge

diff --cc include/net/udplite.h
Simple merge

diff --cc net/ipv4/ip_output.c
Simple merge

diff --cc net/ipv4/ping.c
Simple merge

diff --cc net/ipv4/raw.c
Simple merge

diff --cc net/ipv4/tcp_input.c
Simple merge

diff --cc net/ipv6/raw.c
Simple merge