math: RATIONAL_KUNIT_TEST should depend on RATIONAL instead of selecting it

RATIONAL_KUNIT_TEST selects RATIONAL, thus enabling an optional feature
the user may not want to have enabled.  Fix this by making the test depend
on RATIONAL instead.

Link: https://lkml.kernel.org/r/20210706100945.3803694-3-geert@linux-m68k.org
Fixes: b6c75c4afc ("lib/math/rational: add Kunit test cases")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Trent Piepho <tpiepho@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.debug

@@ -2460,8 +2460,7 @@ config SLUB_KUNIT_TEST
 
 config RATIONAL_KUNIT_TEST
 	tristate "KUnit test for rational.c" if !KUNIT_ALL_TESTS
-	depends on KUNIT
-	select RATIONAL
+	depends on KUNIT && RATIONAL
 	default KUNIT_ALL_TESTS
 	help
 	  This builds the rational math unit test.