[NET]: parse ip:port strings correctly in in4_pton

[NET]: parse ip:port strings correctly in in4_pton

in4_pton converts a textual representation of an ip4 address
into an integer representation. However, when the textual representation
is of in the form ip:port, e.g. 192.168.1.1:5060, and 'delim' is set to
-1, the function bails out with an error when reading the colon.

It makes sense to allow the colon as a delimiting character without
explicitly having to set it through the 'delim' variable as there can be
no ambiguity in the point where the ip address is completely parsed. This
function is indeed called from nf_conntrack_sip.c in this way to parse
textual ip:port combinations which fails due to the reason stated above.

Signed-off-by: Jerome Borsboom <j.borsboom@erasmusmc.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>