net: add documentation to socket.c

net: add documentation to socket.c

Adds missing sphinx documentation to the
socket.c's functions. Also fixes some whitespaces.

I also changed the style of older documentation as an
effort to have an uniform documentation style.

Signed-off-by: Pedro Tammela <pctammela@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>