spi: hisi-kunpeng: Add timeout warning in FIFO flush function

spi: hisi-kunpeng: Add timeout warning in FIFO flush function

When flushing the FIFO, the driver waits for the busy flag to clear
with a timeout. Change the loop condition to use pre-decrement (--limit)
instead of post-decrement (limit--) so that warning message can show. Add a
ratelimited warning message to log SPI busy timeout events, aiding in
debugging.

Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Link: https://patch.msgid.link/dad95ce42fb5677edfed32bc1f9b3e54df2cf8de.1773889292.git.xiaopei01@kylinos.cn
Signed-off-by: Mark Brown <broonie@kernel.org>