lib/Kconfig.debug: TEST_IOV_ITER depends on MMU

In the Linux kernel, the following vulnerability has been resolved:

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.