Finally eradicate CONFIG_HOTPLUG

Ever since commit 45f035ab9b ("CONFIG_HOTPLUG should be always on"),
it has been basically impossible to build a kernel with CONFIG_HOTPLUG
turned off.  Remove all the remaining references to it.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/kbuild/kconfig.txt

@@ -165,7 +165,7 @@ Searching in menuconfig:
 	Example:
 		/hotplug
 		This lists all config symbols that contain "hotplug",
-		e.g., HOTPLUG, HOTPLUG_CPU, MEMORY_HOTPLUG.
+		e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.
 
 	For search help, enter / followed TAB-TAB-TAB (to highlight
 	<Help>) and Enter.  This will tell you that you can also use