cifs: fix IPv6 link local, with scope id, address parsing

When the IP address is gotten from the UNC, use only the address part
of the UNC. Else all after the percent sign in an IPv6 link local
address is interpreted as a scope id. This includes the slash and
share name. A scope id is expected to be an integer and any trailing
characters makes the conversion to integer fail.
Example of mount command that fails:
mount -i -t cifs //fe80::6a05:caff:fe3e:8ffc%2/test /mnt/t -o sec=none

Signed-off-by: Daniel N Pettersson <danielnp@axis.com>
Signed-off-by: Steve French <smfrench@gmail.com>