vga_pci: Allocate resource method requires resource owner CPUID
vga_pci: Fix cached resources cleanup and setup driver's softc size

- The cached resource was not cleanup even if the underlying resource was
  freed.  Now, if the cached resource reference count drops to zero, the
  underlying resource is freed and the cached resource is cleared.
  Submitted-by: dillon@
- The driver uses softc, so the softc size in the driver_t needs to be
  setup properly.