x86: add LongModeAddressSize function to cpuid


LongModeAddressSize was used by kernel 2.6.28.4 for physical address
validation, if not properly implemented, PCI resource allocation may
failed because of ioremap failed:

- linux-2.6.28.4/arch/x86/mm/ioremap.c:27-30
  27 static inline int phys_addr_valid(unsigned long addr)
  28 {
  29     return addr < (1UL << boot_cpu_data.x86_phys_bits);
  30 }

- linux-2.6.28.4/arch/x86/kernel/cpu/common.c:475-482
 475 #ifdef CONFIG_X86_64
 476         if (c->extended_cpuid_level >= 0x80000008) {
 477                 u32 eax = cpuid_eax(0x80000008);
 478
 479                 c->x86_virt_bits = (eax >> 8) & 0xff;
 480                 c->x86_phys_bits = eax & 0xff;
 481         }
 482 #endif

- linux-2.6.28.4/arch/x86/mm/ioremap.c:209-214
 209 if (!phys_addr_valid(phys_addr)) {
 210     printk(KERN_WARNING "ioremap: invalid physical address %llx\n",
 211            (unsigned long long)phys_addr);
 212     WARN_ON_ONCE(1);
 213     return NULL;
 214 }

This patch return 0x0000ffff for LongModeAddressSize, which guarantee phys_addr_valid never failed.