driver: base: Disable CONFIG_UEVENT_HELPER by default

Since commit 7934779a ("Driver-Core: disable /sbin/hotplug by
default"), the help text for the /sbin/hotplug fork-bomb says
"This should not be used today [...] creates a high system load, or
[...] out-of-memory situations during bootup".  The rationale for this
was that no recent mainstream system used this anymore (in 2010!).

A few years later, the complete uevent helper support was made optional
in commit 86d56134 ("kobject: Make support for uevent_helper
optional.").  However, if was still left enabled by default, to support
ancient userland.

Time passed by, and nothing should use this anymore, so it can be
disabled by default.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>