powerpc/pseries: Drop "select HOTPLUG"

The Kconfig symbol HOTPLUG was removed with commit 40b31360 ("Finally
eradicate CONFIG_HOTPLUG"). But there's still one select statement for
that symbol. It seems that select statement was added after the patch to
remove CONFIG_HOTPLUG was submitted. Anyhow, it is useless and can be
dropped.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>