MFC (conceptually) r326752, r326754:

MFC (conceptually) r326752, r326754:

This is a direct commit to 11-stable, because the code has moved and
the directories have been restructured in 12-current, but it just hand-
applies the same patches to the corresponding files in their old locations.

r326752:
  Save and restore r9 register in arm ubldr.  In old gcc 4.2, r9 was a callee-
  saved register, but in arm EABI it may be either callee-saved or dedicated
  to some special purpose (such as a TLS pointer).  It appears clang does not
  treat it as a callee-saved register (instead using it as another work
  register, similar to r12).

  Another important side effect of these changes is that saving an extra
  register in the push/pop statements keeps the stack aligned to an 8-byte
  boundary during the self_reloc() call, as it always should have been.

  As stated in the PR...

  Essentially the important caller-saved registers are pushed (r0, r1, r9, lr)
  before the relocation call, and popped after.  Then r8/r9 are saved as usual
  for the syscall trampoline, and lr is stored in r8 (now free) as a
  callee-saved value before calling into `main`.

  The call to `main` can no longer be a tail call because we must restore r9
  especially after main returns (although since we have used r8 to hold lr we
  must also restore this).

r326754:
  When building for arm arches, set PKTALIGN to the max cache line size
  supported by the arch, to meet u-boot's requirement that I/O be done
  in cache-aligned chunks.

PR:           223977 224008