lib: logic_pio: Avoid possible overlap for unregistering regions

The code was originally written to not support unregistering logical PIO
regions.

To accommodate supporting unregistering logical PIO regions, subtly modify
LOGIC_PIO_CPU_MMIO region registration code, such that the "end" of the
registered regions is the "end" of the last region, and not the sum of
the sizes of all the registered regions.

Cc: stable@vger.kernel.org
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>