arm: Correct comments in crt0.S for the recent SPL improvements

The current comments need a bit of tweaking since we now support stack
and global_data relocation in SPL. Also add a reference to the README.

For AArch64 this is not implemented, so leave a TODO for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Tim Harvey <tharvey@gateworks.com>
2 files changed