drivers:hv: Make a function to free mmio regions through vmbus

drivers:hv: Make a function to free mmio regions through vmbus

BugLink: http://bugs.launchpad.net/bugs/1616677
This patch introduces a function that reverses everything
done by vmbus_allocate_mmio().  Existing code just called
release_mem_region().  Future patches in this series
require a more complex sequence of actions, so this function
is introduced to wrap those actions.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(back ported from commit 97fb77dc87582300fa3c141b63699f853576cab1)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
 Conflicts:
	drivers/hv/vmbus_drv.c
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>