fpga: dfl: map feature mmio resources in their own feature drivers

This patch makes preparation for modularization of DFL sub feature
drivers.

DFL based FPGA devices may contain some IP blocks which are already
supported by kernel, most of them are supported by platform device
drivers. We could create platform devices for these IP blocks and get them
supported by these drivers.

An important issue is that platform device drivers usually requests mmio
resources on probe. But now DFL mmio is mapped in DFL bus driver (e.g.
dfl-pci) as a whole region. Then platform device drivers for sub features
can't request their own mmio resources again. This is what the patch
trying to resolve.

This patch changes the DFL enumeration. DFL bus driver will unmap mmio
resources after first step enumeration and pass enumeration info to DFL
framework. Then DFL framework will map the mmio resources again, do 2nd
step enumeration, and also unmap the mmio resources. In this way, sub
feature drivers could then request their own mmio resources as needed.

An exception is that mmio resource of FIU headers are still mapped in DFL
bus driver. The FIU headers have some fundamental functions (sriov set,
port enable/disable) needed for DFL bus devices and other sub features.
They should not be unmapped as long as DFL bus device is alive.

Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Acked-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>