Revert "riscv: Add a Zalrsc-only alternative for synchronization in start.S"

Revert "riscv: Add a Zalrsc-only alternative for synchronization in start.S"

This reverts commit a681cfecb4346107212f377e2075f6eb1bdc6a2b.

It has been reported that the commit causes boot regression for SPL on
StarFive VisionFive 2 or compatible boards. Inspecting the code, I did
spot one logic error for deciding whether Zaamo or Zalrsc is used, and
it's still unclear what exactly causes the regression, let's revert it
for now.

Reported-by: E Shattow <e@freeshell.de>
Link: https://lore.kernel.org/u-boot/1871663e-b918-4351-9e9e-97f9a4c73733@freeshell.de/
Signed-off-by: Yao Zi <ziyao@disroot.org>
Acked-by: E Shattow <e@freeshell.de>
Acked-by: Leo Yu-Chi Liang <ycliang@andestech.com>