uio: fix dmem_region_start computation

The variable i contains a total number of resources (including
IORESOURCE_IRQ). However, we want the dmem_region_start to point
after the last resource of type IORESOURCE_MEM. The original behaviour
leads (very likely) to skipping several UIO mapping regions and makes
them useless. Fix this by computing dmem_region_start from the uiomem
which points to the last used UIO mapping.

Fixes: 0a0c3b5a ("Add new uio device for dynamic memory allocation")

Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>