When ld detects unaligned relocations, it emits R_PPC64_UADDR64
relocations instead of R_PPC64_RELATIVE. Currently R_PPC64_UADDR64 are
detected by arch/powerpc/tools/relocs_check.sh and expected not to work.
Below is a simple chunk to trigger this behaviour (this disables
optimization for the demonstration purposes only, this also happens with
-O1/-O2 when CONFIG_PRINTK_INDEX=y, for example):

  \#pragma GCC push_options
  \#pragma GCC optimize ("O0")
  struct entry {
          const char *file;
          int line;
  } __attribute__((packed));
  static const struct entry e1 = { .file = __FILE__, .line = __LINE__ };
  static const struct entry e2 = { .file = __FILE__, .line = __LINE__ };
  ...
  prom_printf("e1=%s %lx %lx\n", e1.file, (unsigned long) e1.file, mfmsr());
  prom_printf("e2=%s %lx\n", e2.file, (unsigned long) e2.file);
  \#pragma GCC pop_options

This adds support for UADDR64 for 64bit. This reuses __dynamic_symtab
from the 32bit code which supports more relocation types already.

Because RELACOUNT includes only R_PPC64_RELATIVE, this replaces it with
RELASZ which is the size of all relocation records.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220309061822.168173-1-aik@ozlabs.ru