Revert "Align global_data to a 16-byte boundary"

This causes widespread breakage due to the operation of the low-level code
in crt0.S and cro0_64.S for ARM at least.

The fix is not complicated but it seems safer to revert this for now.

This reverts commit 2afddae0.
Signed-off-by: Simon Glass <sjg@chromium.org>