[PATCH v9 55/60] PCI, x86: Allocate from high in available window for MMIO

Current code just use aligned start from avialable window, that could waste big alignment from start. We can align to the end from avialable window, so will save start with big align to others: like second try for pref mmio after first try already have non-pref assigned. pci tree:

[PATCH v9 55/60] PCI, x86: Allocate from high in available window for MMIO

Current code just use aligned start from avialable window, that could waste big alignment from start. We can align to the end from avialable window, so will save start with big align to others: like second try for pref mmio after first try already have non-pref assigned. pci tree: