net: Remove the deprecated -tftp, -bootp, -redir and -smb options

These options likely do not work as expected as soon as the user
tries to use more than one network interface at once. The parameters
have been marked as deprecated since QEMU v2.6, so users had plenty
of time to move their scripts to the new syntax. Time to remove the
old parameters now.

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>