devres: implement pcim_iomap_regions()

Implement pcim_iomap_regions().  This function takes mask of BARs to
request and iomap.  No BAR should have length of zero.  BARs are
iomapped using pcim_iomap_table().

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>