staging: unisys: visorbus: move parahotplug_request_list and related lock

parahotplug_request_list and parahotplug_request_list_lock should be
defined closer to where we are actually using them.

Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>