lib/Kconfig.debug: TEST_IOV_ITER depends on MMU

Trying to run the iov_iter unit test on a nommu system such as the qemu
kc705-nommu emulation results in a crash.

    KTAP version 1
    # Subtest: iov_iter
    # module: kunit_iov_iter
    1..9
BUG: failure at mm/nommu.c:318/vmap()!
Kernel panic - not syncing: BUG!

The test calls vmap() directly, but vmap() is not supported on nommu
systems, causing the crash.  TEST_IOV_ITER therefore needs to depend on
MMU.

Link: https://lkml.kernel.org/r/20240208153010.1439753-1-linux@roeck-us.net
Fixes: 2d71340f ("iov_iter: Kunit tests for copying to/from an iterator")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/Kconfig.debug

@@ -2235,6 +2235,7 @@ config TEST_DIV64
 config TEST_IOV_ITER
 	tristate "Test iov_iter operation" if !KUNIT_ALL_TESTS
 	depends on KUNIT
+	depends on MMU
 	default KUNIT_ALL_TESTS
 	help
 	  Enable this to turn on testing of the operation of the I/O iterator