slirp: Use g_new() to allocate sockets in socreate()

slirp: Use g_new() to allocate sockets in socreate()

The slirp socreate() function can only fail if the attempt
to malloc() the struct socket fails. Switch to using
g_new() instead, which will allow us to remove the
error-handling code from its callers.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>