driver core: Make Kconfig text for DEBUG_TEST_DRIVER_REMOVE stronger

The current state of driver removal is not great.
CONFIG_DEBUG_TEST_DRIVER_REMOVE finds lots of errors. The help text
currently undersells exactly how many errors this option will find. Add
a bit more description to indicate this option shouldn't be turned on
unless you actually want to debug driver removal. The text can be
changed later when more drivers are fixed up.

Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>