mptcp: MPTCP_KUNIT_TESTS should depend on MPTCP instead of selecting it

MPTCP_KUNIT_TESTS selects MPTCP, thus enabling an optional feature the
user may not want to enable.  Fix this by making the test depend on
MPTCP instead.

Fixes: a00a5822 ("mptcp: move crypto test to KUNIT")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Link: https://lore.kernel.org/r/20201019113240.11516-1-geert@linux-m68k.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/Kconfig

@@ -22,11 +22,8 @@ config MPTCP_IPV6
 	select IPV6
 	default y
 
-endif
-
 config MPTCP_KUNIT_TESTS
 	tristate "This builds the MPTCP KUnit tests" if !KUNIT_ALL_TESTS
-	select MPTCP
 	depends on KUNIT
 	default KUNIT_ALL_TESTS
 	help
@@ -39,3 +36,4 @@ config MPTCP_KUNIT_TESTS
 
 	  If unsure, say N.
 
+endif