Enable Multipath TCP support

See https://www.mptcp.dev/ for MPTCP details and OTP 27.3.4.6 for use
when Erlang.

Author: fhunleth

linux/linux-6.12.defconfig

@@ -30,6 +30,7 @@ CONFIG_INET=y
 CONFIG_IP_MULTICAST=y
 CONFIG_IP_ADVANCED_ROUTER=y
 CONFIG_IP_MULTIPLE_TABLES=y
+CONFIG_MPTCP=y
 CONFIG_BRIDGE=m
 CONFIG_NET_SCHED=y
 CONFIG_VSOCKETS=y