net: reject creation of netdev names with colons

colons are used as a separator in netdev device lookup in dev_ioctl.c

Specific functions are SIOCGIFTXQLEN SIOCETHTOOL SIOCSIFNAME

Signed-off-by: Matthew Thode <mthode@mthode.org>
Signed-off-by: David S. Miller <davem@davemloft.net>