Revert "target/image: zero-initialize ELF segments up to p_memsz"

Revert "target/image: zero-initialize ELF segments up to p_memsz"

This reverts commit 047b1a8fc237af480e3bab66a9827a358afd7547.

Commit 047b1a8fc237 ("target/image: zero-initialize ELF segments
up to p_memsz") breaks the backward compatibility introducing some
problem:
- an empty bss segment with paddr in SRAM gets zero filled at load
  but does not survive after a reset, causing verify to fail;
- an empty bss segment with paddr in FLASH causes excessive flash
  usage, which can exceed flash size (causing error) and makes
  flash aging faster.

Revert it while looking for a better implementation.

Change-Id: Iaaf926dafce46a220a5bbe20c8576eb449996d76
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reported-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/7658
Reviewed-by: Bohdan Tymkiv <bohdan200@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Nemui Trinomius <nemuisan_kawausogasuki@live.jp>
Reviewed-by: Peter Collingbourne <pcc@google.com>
Tested-by: jenkins