vgapci: Use vga_pci_alloc_resource() to map PCI Expansion ROM

This is cleaner and fixes Video BIOS mapping when the given device isn't
the boot display.

Submitted by:	jhb@
Approved by:	re (kib)
drm/radeon: Fix usage of vga_pci_map_bios()

vga_pci_(un)map_bios() takes a vgapci device as argument, not a drmn
one. This fixes a bug where the BIOS couldn't be mapped if the device
wasn't the boot display.

Approved by:	re (kib; blanket for following drm2/radeon commits)
drm/radeon: Fix usage of pci_save_state() and pci_restore_state()

Calling those functions with the drmn device as argument causes a panic,
because it's not a direct child of pci$N. They must be called with the
vgapci device instead.

This fix is not enough to make suspend/resume work reliably.

Approved by:	re (blanket)