hw/pci-stub: fix comment typo

[Stefan fixed "doesn't" -> "don't"]
Signed-off-by: NAlon Levy <alevy@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

hw/pci-stub.c

 /*
- * PCI stubs for plathome that doesn't support pci bus.
+ * PCI stubs for platforms that don't support pci bus.
  *
  * Copyright (c) 2010 Isaku Yamahata <yamahata at valinux co jp>
  *                    VA Linux Systems Japan K.K.