resource: Export find_resource_space()

PCI bridge window logic needs to find out in advance to the actual
allocation if there is an empty space big enough to fit the window.

Export find_resource_space() for the purpose. Also move the struct
resource_constraint into generic header to be able to use the new
interface.

Link: https://lore.kernel.org/r/20240507102523.57320-7-ilpo.jarvinen@linux.intel.com


Tested-by: Lidong Wang <lidong.wang@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>