vsio -> vsio6

This will allow vsio to be used for DHCP in a separate option space.

src/dhcpcd.conf.5.in

@@ -782,7 +782,7 @@ Set the vendor option 03 with an IP address as a string.
 .D1 vendor 03,\e"192.168.0.2\e"
 Set un-encapsulated vendor option to hello world.
 .D1 vendor ,"hello world"
-.It Ic vsio Ar en Ar code, Ns Ar value
+.It Ic vsio6 Ar en Ar code, Ns Ar value
 Add an encapsulated vendor-specific information option (DHCPv6 Option 17) with
 IANA assigned Enterprise Number
 .Ar en
@@ -793,11 +793,11 @@ which should be between 1 and 65535 inclusive, and the
 after the comma. Examples:
 .Pp
 Set the vsio for enterprise number 155 option 01 with an IPv6 address.
-.D1 vsio 155 01,2001:0db8:85a3:0000:0000:8a2e:0370:7334
+.D1 vsio6 155 01,2001:0db8:85a3:0000:0000:8a2e:0370:7334
 Set the vsio for enterprise number 155 option 02 with a string.
-.D1 vsio 155 02,"hello world"
+.D1 vsio6 155 02,"hello world"
 Set the vsio for enterprise number 255 option 01 with a hex code.
-.D1 vsio 255 01,01:02:03:04:05
+.D1 vsio6 255 01,01:02:03:04:05
 .It Ic vendorclassid Ar string
 Set the DHCP Vendor Class.
 DHCPv6 has its own option as shown below.

src/if-options.c

@@ -87,7 +87,7 @@ const struct option cf_options[] = {
 #ifndef SMALL
 	{"msuserclass",     required_argument, NULL, O_MSUSERCLASS},
 #endif
-	{"vsio",            required_argument, NULL, O_VENDOPT6},
+	{"vsio6",           required_argument, NULL, O_VENDOPT6},
 	{"vendor",          required_argument, NULL, 'v'},
 	{"waitip",          optional_argument, NULL, 'w'},
 	{"exit",            no_argument,       NULL, 'x'},