CONFIG_HOTPLUG should be always on

CONFIG_HOTPLUG is a very old option, back when we had static systems and it was
odd that any type of device would be removed or added after the system had
started up.  It is quite hard to disable it these days, and even if you do, it
only saves you about 200 bytes.  However, if it is disabled, lots of bugs show
up because it is almost never tested if the option is disabled.

This is a step to eventually just remove the option entirely, which will clean
up all of the devinit* variable and function pointer options, that everyone
(myself include) ends up getting wrong eventually, causing real problems when
memory segments are removed yet we don't expect them to be.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>