cnic: Fix mmap regression.

commit 1f85d58cdf15354a7120fc9ccc9bb9c45b53af88
    cnic: Remove uio mem[0].

introduced a regression as older versions of userspace app still rely
on this mmap.  Restore the mmap functionality and get the base address
from pci_resource_start() as the nedev->base_addr has been deprecated for
PCI devices.

Update version to 2.5.12.

Signed-off-by: Michael Chan <mchan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>