xtensa: remove duplicate CONFIG_HOTPLUG definition

As part of the plan to remove CONFIG_HOTPLUG, it was found that xtensa
duplicates this config option for no reason (it's already defined as part of
init/Kconfig).  This patch removes it from the xtensa-only Kconfig file.

Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>