Commit
a375282ae9d3ea161146a998d3a0ae0a4b5efa7c
by Pau Espin Pedrolosmo_io.h: Avoid including sys/socket.h
sys/socket.h may not always be available (eg. arm-none-eabi toolchain).
In the header file we only really need the forward declaration of struct
msghdr, so simply do that.
Change-Id: I5bcba8f72a2be6161d7782a3100d25a7025341d0
