ARM: shmobile: defconfig: Disable /sbin/hotplug fork-bomb

No recent mainstream system uses the /sbin/hotplug fork-bomb any more.
Commit 7934779a ("Driver-Core: disable
/sbin/hotplug by default") disabled it in Kconfig, but the various
defconfigs weren't updated.

According to the systemd requirements, this option must be disabled, as
it slows down the system and confuses udev.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>