mptcp: fix Kconfig warning

  net/mptcp/Kconfig:62:warning: choice default symbol 'DEFAULT' is not contained in the choice
  net/mptcp/Kconfig:124:warning: choice default symbol 'DEFAULT' is not contained in the choice

Also removed a trailing whitespace introduces in the same commit.

Note that it would be nice to prefix all these "DEFAULT_xxx" with
"MPTCP_" and even "MPTCP_PM_" / "MPTCP_SCHED_" because it is not obvious
to know what they are when you see that in the .config:

  CONFIG_DEFAULT_DUMMY
  CONFIG_DEFAULT_FULLMESH
  CONFIG_DEFAULT_SCHEDULER
  (...)

But I guess it is too late and it should not conflicts with new kconfig
because they should always be prefixed with something.

Fixes: 54d8697 (Modularize the path-manager)
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
(cherry picked from commit 1efcfb3)
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
(cherry picked from commit b56d4e2)
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>

net/mptcp/Kconfig

@@ -41,7 +41,7 @@ config MPTCP_BINDER
 
 choice
 	prompt "Default MPTCP Path-Manager"
-	default DEFAULT
+	default DEFAULT_DUMMY
 	help
 	  Select the Path-Manager of your choice
 
@@ -64,7 +64,7 @@ endif
 config DEFAULT_MPTCP_PM
 	string
 	default "default" if DEFAULT_DUMMY
-	default "fullmesh" if DEFAULT_FULLMESH 
+	default "fullmesh" if DEFAULT_FULLMESH
 	default "ndiffports" if DEFAULT_NDIFFPORTS
 	default "binder" if DEFAULT_BINDER
 	default "default"
@@ -94,7 +94,7 @@ config MPTCP_REDUNDANT
 
 choice
 	prompt "Default MPTCP Scheduler"
-	default DEFAULT
+	default DEFAULT_SCHEDULER
 	help
 	  Select the Scheduler of your choice