[ubsan] fix some bugs and warnings discovered by ubsan

- X86 cpuid feature list dump was using the wrong array and walking off
  the end of one.
- GICv2 code had a left shift by up to 31 of an integer. Needs to be
  unsigned.
- PLIC same as GIC code.
- fdtwalker code should be using a bytewise accessor based helper
  function for reading large integers out of an unaliged FDT.
- PCI BIOS32 search code could do a 32bit unaligned read of a string,
  switch to using memcmp.

arch/x86/feature.c

@@ -229,7 +229,7 @@ static void x86_feature_dump_cpuid(void) {
     for (uint32_t i = X86_CPUID_EXT_BASE; i <= max_cpuid_leaf_ext; i++) {
         uint32_t index = i - X86_CPUID_EXT_BASE;
         printf("X86: cpuid leaf %#x: %08x %08x %08x %08x\n", i,
-               saved_cpuids[index].a, saved_cpuids[index].b, saved_cpuids[index].c, saved_cpuids[index].d);
+               saved_cpuids_ext[index].a, saved_cpuids_ext[index].b, saved_cpuids_ext[index].c, saved_cpuids_ext[index].d);
     }
 }
 

arch/x86/include/arch/x86/feature.h

@@ -105,7 +105,8 @@ enum x86_cpuid_leaf_num {
   X86_CPUID_BRAND = 0x80000002,
   X86_CPUID_ADDR_WIDTH = 0x80000008,
   X86_CPUID_AMD_TOPOLOGY = 0x8000001e,
-  __X86_MAX_SUPPORTED_CPUID_EXT = X86_CPUID_AMD_TOPOLOGY,
+  X86_CPUID_AMD_EXTENDED_TOPOLOGY = 0x80000025,
+  __X86_MAX_SUPPORTED_CPUID_EXT = X86_CPUID_AMD_EXTENDED_TOPOLOGY,
 };
 
 struct x86_cpuid_bit {